diff --git a/packages/ERTP/test/unitTests/mathHelpers/test-natMathHelpers.js b/packages/ERTP/test/unitTests/mathHelpers/test-natMathHelpers.js
index a40f801ea1e..69be9687ed3 100644
--- a/packages/ERTP/test/unitTests/mathHelpers/test-natMathHelpers.js
+++ b/packages/ERTP/test/unitTests/mathHelpers/test-natMathHelpers.js
@@ -19,13 +19,13 @@ test('natMathHelpers make', t => {
   t.throws(
     () => m.make('abc', mockBrand),
     {
-      message: 'value (a string) must be a Nat or an array',
+      message: /value .* must be a Nat or an array/,
     },
     `'abc' is not a nat`,
   );
   t.throws(
     () => m.make(-1, mockBrand),
-    { message: 'value (a number) must be a Nat or an array' },
+    { message: /value .* must be a Nat or an array/ },
     `- 1 is not a valid Nat`,
   );
 });
@@ -34,7 +34,7 @@ test('natMathHelpers make no brand', t => {
   t.throws(
     () => m.make(4n),
     {
-      message: "The brand (an undefined) doesn't look like a brand.",
+      message: /The brand "\[undefined\]" doesn't look like a brand./,
     },
     `brand is required in make`,
   );
@@ -70,7 +70,7 @@ test('natMathHelpers coerce', t => {
   t.throws(
     () => m.coerce(3n, mockBrand),
     {
-      message: `The amount (a bigint) doesn't look like an amount. Did you pass a value instead?`,
+      message: /The amount .* doesn't look like an amount. Did you pass a value instead?/,
     },
     `coerce needs a brand`,
   );
@@ -81,7 +81,7 @@ test('natMathHelpers coerce no brand', t => {
     // @ts-ignore deliberate invalid arguments for testing
     () => m.coerce(m.make(4n, mockBrand)),
     {
-      message: "The brand (an undefined) doesn't look like a brand.",
+      message: /The brand "\[undefined\]" doesn't look like a brand./,
     },
     `brand is required in coerce`,
   );
@@ -97,7 +97,7 @@ test('natMathHelpers getValue no brand', t => {
     // @ts-ignore deliberate invalid arguments for testing
     () => m.getValue(m.make(4n, mockBrand)),
     {
-      message: "The brand (an undefined) doesn't look like a brand.",
+      message: /The brand "\[undefined\]" doesn't look like a brand./,
     },
     `brand is required in getValue`,
   );
@@ -114,7 +114,7 @@ test('natMathHelpers makeEmpty no brand', t => {
     // @ts-ignore deliberate invalid arguments for testing
     () => m.makeEmpty(MathKind.NAT),
     {
-      message: "The brand (a string) doesn't look like a brand.",
+      message: /The brand .* doesn't look like a brand./,
     },
     `make empty no brand`,
   );
@@ -128,21 +128,21 @@ test('natMathHelpers isEmpty', t => {
   t.throws(
     () => m.isEmpty('abc'),
     {
-      message: `The amount (a string) doesn't look like an amount. Did you pass a value instead?`,
+      message: /The amount .* doesn't look like an amount. Did you pass a value instead?/,
     },
     `isEmpty('abc') throws because it cannot be coerced`,
   );
   t.throws(
     () => m.isEmpty({ brand: mockBrand, value: 'abc' }),
     {
-      message: 'value (a string) must be a Nat or an array',
+      message: /value .* must be a Nat or an array/,
     },
     `isEmpty('abc') throws because it cannot be coerced`,
   );
   t.throws(
     () => m.isEmpty(0n),
     {
-      message: `The amount (a bigint) doesn't look like an amount. Did you pass a value instead?`,
+      message: /The amount .* doesn't look like an amount. Did you pass a value instead?/,
     },
     `isEmpty(0) throws because it cannot be coerced`,
   );
@@ -161,8 +161,7 @@ test('natMathHelpers isGTE mixed brands', t => {
   t.throws(
     () => m.isGTE(m.make(5n, Far('otherBrand', {})), m.make(3n, mockBrand)),
     {
-      message:
-        'Brands in left (an object) and right (an object) should match but do not',
+      message: /Brands in left .* and right .* should match but do not/,
     },
   );
 });
@@ -176,8 +175,7 @@ test(`natMathHelpers isGTE - brands don't match objective brand`, t => {
         Far('otherBrand', {}),
       ),
     {
-      message:
-        "amount's brand (an object) did not match expected brand (an object)",
+      message: /amount's brand .* did not match expected brand .*/,
     },
   );
 });
@@ -197,8 +195,7 @@ test('natMathHelpers isEqual mixed brands', t => {
   t.throws(
     () => m.isEqual(m.make(4n, Far('otherBrand', {})), m.make(4n, mockBrand)),
     {
-      message:
-        'Brands in left (an object) and right (an object) should match but do not',
+      message: /Brands in left .* and right .* should match but do not/,
     },
   );
 });
@@ -212,8 +209,7 @@ test(`natMathHelpers isEqual - brands don't match objective brand`, t => {
         Far('otherBrand', {}),
       ),
     {
-      message:
-        "amount's brand (an object) did not match expected brand (an object)",
+      message: /amount's brand .* did not match expected brand .*/,
     },
   );
 });
@@ -230,8 +226,7 @@ test('natMathHelpers add mixed brands', t => {
   t.throws(
     () => m.add(m.make(5n, Far('otherBrand', {})), m.make(9n, mockBrand)),
     {
-      message:
-        'Brands in left (an object) and right (an object) should match but do not',
+      message: /Brands in left .* and right .* should match but do not/,
     },
   );
 });
@@ -245,8 +240,7 @@ test(`natMathHelpers add - brands don't match objective brand`, t => {
         Far('otherBrand', {}),
       ),
     {
-      message:
-        "amount's brand (an object) did not match expected brand (an object)",
+      message: /amount's brand .* did not match expected brand .*/,
     },
   );
 });
@@ -263,8 +257,7 @@ test('natMathHelpers subtract mixed brands', t => {
   t.throws(
     () => m.subtract(m.make(6n, Far('otherBrand', {})), m.make(1n, mockBrand)),
     {
-      message:
-        'Brands in left (an object) and right (an object) should match but do not',
+      message: /Brands in left .* and right .* should match but do not/,
     },
   );
 });
@@ -278,8 +271,7 @@ test(`natMathHelpers subtract brands don't match brand`, t => {
         Far('otherBrand', {}),
       ),
     {
-      message:
-        "amount's brand (an object) did not match expected brand (an object)",
+      message: /amount's brand .* did not match expected brand .*/,
     },
   );
 });
diff --git a/packages/ERTP/test/unitTests/mathHelpers/test-setMathHelpers.js b/packages/ERTP/test/unitTests/mathHelpers/test-setMathHelpers.js
index d0927bc0f61..188fc41a014 100644
--- a/packages/ERTP/test/unitTests/mathHelpers/test-setMathHelpers.js
+++ b/packages/ERTP/test/unitTests/mathHelpers/test-setMathHelpers.js
@@ -48,7 +48,7 @@ const runSetMathHelpersTests = (t, [a, b, c], a2 = undefined) => {
   );
   t.throws(
     () => m.make('a', mockBrand),
-    { message: `value (a string) must be a Nat or an array` },
+    { message: /value .* must be a Nat or an array/ },
     'strings are not valid',
   );
   if (a2 !== undefined) {
@@ -87,7 +87,7 @@ const runSetMathHelpersTests = (t, [a, b, c], a2 = undefined) => {
   );
   t.throws(
     () => m.coerce({ brand: mockBrand, value: 'a' }, mockBrand),
-    { message: `value (a string) must be a Nat or an array` },
+    { message: /value .* must be a Nat or an array/ },
     'strings are not valid',
   );
   if (a2 !== undefined) {
@@ -119,7 +119,7 @@ const runSetMathHelpersTests = (t, [a, b, c], a2 = undefined) => {
   );
   t.throws(
     () => m.isEmpty({ brand: mockBrand, value: harden({}) }),
-    { message: `value (an object) must be a Nat or an array` },
+    { message: /value .* must be a Nat or an array/ },
     `m.isEmpty({}) throws`,
   );
   t.falsy(m.isEmpty(m.make(['abc'], mockBrand)), `m.isEmpty(['abc']) is false`);
diff --git a/packages/ERTP/test/unitTests/mathHelpers/test-strSetMathHelpers.js b/packages/ERTP/test/unitTests/mathHelpers/test-strSetMathHelpers.js
index bc8e561acf7..a8465ab386f 100644
--- a/packages/ERTP/test/unitTests/mathHelpers/test-strSetMathHelpers.js
+++ b/packages/ERTP/test/unitTests/mathHelpers/test-strSetMathHelpers.js
@@ -20,7 +20,7 @@ test('set with strings make', t => {
   );
   t.throws(
     () => m.make('abc', mockBrand),
-    { message: `value (a string) must be a Nat or an array` },
+    { message: /value .* must be a Nat or an array/ },
     `'abc' is not a valid string array`,
   );
   t.throws(
@@ -42,7 +42,7 @@ test('set with strings coerce', t => {
   );
   t.throws(
     () => m.coerce({ brand: mockBrand, value: '6' }, mockBrand),
-    { message: `value (a string) must be a Nat or an array` },
+    { message: /value .* must be a Nat or an array/ },
     `'6' is not a valid array`,
   );
   t.throws(
@@ -71,7 +71,7 @@ test('set with strings makeEmpty', t => {
   );
   t.throws(
     () => m.isEmpty({ brand: mockBrand, value: ['a', 'a'] }),
-    { message: `value has duplicates: (a string) and (a string)` },
+    { message: /value has duplicates: .* and .*/ },
     `duplicates in isEmpty throw`,
   );
 });
@@ -185,7 +185,7 @@ test('set with strings add', t => {
         { brand: mockBrand, value: ['a'] },
         { brand: mockBrand, value: ['a'] },
       ),
-    { message: `value has duplicates: (a string) and (a string)` },
+    { message: /value has duplicates: .* and .*/ },
     `overlap between left and right of add should throw`,
   );
   t.deepEqual(
@@ -231,7 +231,7 @@ test('set with strings subtract', t => {
         { brand: mockBrand, value: ['a', 'b'] },
         { brand: mockBrand, value: ['c'] },
       ),
-    { message: `right element (a string) was not in left` },
+    { message: /right element .* was not in left/ },
     `elements in right but not in left of subtract should throw`,
   );
   t.deepEqual(
diff --git a/packages/ERTP/test/unitTests/test-issuerObj.js b/packages/ERTP/test/unitTests/test-issuerObj.js
index c781833ac60..35507d89026 100644
--- a/packages/ERTP/test/unitTests/test-issuerObj.js
+++ b/packages/ERTP/test/unitTests/test-issuerObj.js
@@ -45,7 +45,12 @@ test('bad display info', t => {
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => makeIssuerKit('fungible', MathKind.NAT, displayInfo), {
     message:
-      'key "somethingUnexpected" was not one of the expected keys ["decimalPlaces"]',
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /key "somethingUnexpected" was not one of the expected keys \["decimalPlaces"\]/,
+      /key .* was not one of the expected keys .*/,
   });
 });
 
@@ -415,7 +420,15 @@ test('issuer.combine bad payments', async t => {
 
   await t.throwsAsync(
     () => E(issuer).combine(payments),
-    { message: /"payment" not found/ },
+    {
+      message:
+        // Should be able to use more informative error once SES double
+        // disclosure bug is fixed. See
+        // https://github.com/endojs/endo/pull/640
+        //
+        // /"payment" not found/
+        /.* not found/,
+    },
     'payment from other mint is not found',
   );
 });
diff --git a/packages/SwingSet/package.json b/packages/SwingSet/package.json
index 5c2bb0c9e05..764578d23bf 100644
--- a/packages/SwingSet/package.json
+++ b/packages/SwingSet/package.json
@@ -59,7 +59,7 @@
     "rollup": "^1.23.1",
     "rollup-plugin-node-resolve": "^5.2.0",
     "semver": "^6.3.0",
-    "ses": "^0.12.3",
+    "ses": "^0.12.5",
     "yargs": "^14.2.0"
   },
   "files": [
diff --git a/packages/assert/package.json b/packages/assert/package.json
index cf3cb190c39..e0b31fbbd9f 100755
--- a/packages/assert/package.json
+++ b/packages/assert/package.json
@@ -68,6 +68,6 @@
     "access": "public"
   },
   "dependencies": {
-    "ses": "^0.12.3"
+    "ses": "^0.12.5"
   }
 }
diff --git a/packages/dapp-svelte-wallet/api/test/test-lib-dehydrate.js b/packages/dapp-svelte-wallet/api/test/test-lib-dehydrate.js
index 2eda1559f81..0e6c8632249 100644
--- a/packages/dapp-svelte-wallet/api/test/test-lib-dehydrate.js
+++ b/packages/dapp-svelte-wallet/api/test/test-lib-dehydrate.js
@@ -18,7 +18,7 @@ test('makeDehydrator', async t => {
   instanceHandleMapping.addPetname('atomicSwap', handle2);
   instanceHandleMapping.addPetname('automaticRefund', handle3);
   t.throws(() => instanceHandleMapping.addPetname('simpleExchange2', handle1), {
-    message: /val \(an object\) already has a petname/,
+    message: /val .* already has a petname/,
   });
   t.throws(
     () =>
@@ -26,7 +26,7 @@ test('makeDehydrator', async t => {
         'simpleExchange',
         Far('simpleExchangeHandle'),
       ),
-    { message: /petname \(a string\) is already in use/ },
+    { message: /petname .* is already in use/ },
   );
 
   // Test renaming.
@@ -77,7 +77,15 @@ test('makeDehydrator', async t => {
   instanceHandleMapping.deletePetname('to be deleted');
   t.throws(
     () => instanceHandleMapping.petnameToVal.get('to be deleted'),
-    { message: /"petname" not found/ },
+    {
+      message:
+        // Should be able to use more informative error once SES double
+        // disclosure bug is fixed. See
+        // https://github.com/endojs/endo/pull/640
+        //
+        // /"petname" not found/
+        /.* not found/,
+    },
     `can't get what has been deleted`,
   );
 
diff --git a/packages/dapp-svelte-wallet/api/test/test-lib-wallet.js b/packages/dapp-svelte-wallet/api/test/test-lib-wallet.js
index 561980f10bd..0cc8e79ec6a 100644
--- a/packages/dapp-svelte-wallet/api/test/test-lib-wallet.js
+++ b/packages/dapp-svelte-wallet/api/test/test-lib-wallet.js
@@ -472,7 +472,15 @@ test('lib-wallet dapp suggests issuer, instance, installation petnames', async t
 
   t.throws(
     () => wallet.getInstallation('whatever'),
-    { message: /"petname" not found/ },
+    {
+      message:
+        // Should be able to use more informative error once SES double
+        // disclosure bug is fixed. See
+        // https://github.com/endojs/endo/pull/640
+        //
+        // /"petname" not found/
+        /.* not found/,
+    },
     `using a petname that doesn't exist errors`,
   );
 
diff --git a/packages/dapp-svelte-wallet/ui/package.json b/packages/dapp-svelte-wallet/ui/package.json
index 8f43f24c118..f36c2e21191 100644
--- a/packages/dapp-svelte-wallet/ui/package.json
+++ b/packages/dapp-svelte-wallet/ui/package.json
@@ -24,7 +24,7 @@
     "rollup-plugin-livereload": "^1.0.0",
     "rollup-plugin-svelte": "^5.0.3",
     "rollup-plugin-terser": "^6.1.0",
-    "ses": "^0.12.3",
+    "ses": "^0.12.5",
     "sirv-cli": "^1.0.0",
     "smelte": "^1.0.15",
     "svelte": "^3.0.0",
diff --git a/packages/deploy-script-support/test/unitTests/test-assertOfferResult.js b/packages/deploy-script-support/test/unitTests/test-assertOfferResult.js
index 80ed2025601..fba33d3f4bd 100644
--- a/packages/deploy-script-support/test/unitTests/test-assertOfferResult.js
+++ b/packages/deploy-script-support/test/unitTests/test-assertOfferResult.js
@@ -12,6 +12,6 @@ test('assertOfferResult', async t => {
   };
   await t.notThrowsAsync(() => assertOfferResult(mockSeat, 'result'));
   await t.throwsAsync(() => assertOfferResult(mockSeat, 'not result'), {
-    message: 'offerResult ((a string)) did not equal expected: (a string)',
+    message: /offerResult (.*) did not equal expected: .*/,
   });
 });
diff --git a/packages/install-ses/package.json b/packages/install-ses/package.json
index f5307e4ff6e..982b8488a2e 100644
--- a/packages/install-ses/package.json
+++ b/packages/install-ses/package.json
@@ -20,7 +20,7 @@
   },
   "dependencies": {
     "@agoric/eventual-send": "^0.13.4",
-    "ses": "^0.12.3"
+    "ses": "^0.12.5"
   },
   "files": [
     "src/**/*.js"
diff --git a/packages/spawner/test/swingsetTests/escrow/test-escrow.js b/packages/spawner/test/swingsetTests/escrow/test-escrow.js
index 0b09c28159c..6dd28c4dc30 100644
--- a/packages/spawner/test/swingsetTests/escrow/test-escrow.js
+++ b/packages/spawner/test/swingsetTests/escrow/test-escrow.js
@@ -21,7 +21,7 @@ test.skip('escrow checkUnits w/SES', async t => {
 
 const escrowMismatchGolden = [
   'starting testEscrowServiceCheckMismatches',
-  'expected unsuccessful check Error: Escrow checkUnits: different at top.right.value: ((a string)) vs ((a string))',
+  /expected unsuccessful check Error: Escrow checkUnits: different at top.right.value: (.*) vs (.*)/,
 ];
 
 test.skip('escrow check misMatches w/SES', async t => {
@@ -31,7 +31,7 @@ test.skip('escrow check misMatches w/SES', async t => {
 
 const escrowCheckPartialWrongPriceGolden = [
   'starting testEscrowServiceCheckPartial wrong price',
-  'expected wrong price Error: Escrow checkPartialUnits seat: different at top.value: ((a number)) vs ((a number))',
+  /expected wrong price Error: Escrow checkPartialUnits seat: different at top.value: (.*) vs (.*)/,
 ];
 
 test.skip('escrow check partial price misMatches w/SES', async t => {
@@ -41,7 +41,7 @@ test.skip('escrow check partial price misMatches w/SES', async t => {
 
 const escrowCheckPartialWrongStockGolden = [
   'starting testEscrowServiceCheckPartial wrong stock',
-  'expected wrong stock Error: Escrow checkPartialUnits seat: different at top.value: ((a string)) vs ((a string))',
+  /expected wrong stock Error: Escrow checkPartialUnits seat: different at top.value: (.*) vs (.*)/,
 ];
 
 test.skip('escrow check partial stock misMatches w/SES', async t => {
@@ -51,7 +51,7 @@ test.skip('escrow check partial stock misMatches w/SES', async t => {
 
 const escrowCheckPartialWrongSeatGolden = [
   'starting testEscrowServiceCheckPartial wrong seat',
-  'expected wrong side Error: Escrow checkPartialUnits seat: label not found on right at top: ((an object)) vs ((an object))',
+  /expected wrong side Error: Escrow checkPartialUnits seat: label not found on right at top: (.*) vs (.*)/,
 ];
 
 test.skip('escrow check partial wrong seat w/SES', async t => {
diff --git a/packages/store/test/test-store.js b/packages/store/test/test-store.js
index 440ac506165..791b08c8331 100644
--- a/packages/store/test/test-store.js
+++ b/packages/store/test/test-store.js
@@ -44,7 +44,13 @@ function check(t, mode, objMaker) {
   checkEntries([[k1, 'one']]);
 
   t.throws(() => s.init(k1, 'other'), {
-    message: /"store1" already registered:/,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"store1" already registered:/,
+      /.* already registered:/,
   });
   t.throws(() => s.get(k2), { message: /"store1" not found:/ });
   t.throws(() => s.set(k2, 'other'), { message: /"store1" not found:/ });
diff --git a/packages/ui-components/test/display/natValue/test-captureNum.js b/packages/ui-components/test/display/natValue/test-captureNum.js
index 5eb45ff4a96..448b0cf8694 100644
--- a/packages/ui-components/test/display/natValue/test-captureNum.js
+++ b/packages/ui-components/test/display/natValue/test-captureNum.js
@@ -13,24 +13,24 @@ test('captureNum', t => {
 
 test('captureNum neg num throws', t => {
   t.throws(() => captureNum('-200'), {
-    message: '(a string) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
   t.throws(() => captureNum('-200.00'), {
-    message: '(a string) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
   t.throws(() => captureNum('-0200.00'), {
-    message: '(a string) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
   t.throws(() => captureNum('-200.020'), {
-    message: '(a string) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
 });
 
 test('captureNum non-number throws', t => {
   t.throws(() => captureNum('a'), {
-    message: '(a string) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
   t.throws(() => captureNum({}), {
-    message: '(an object) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
 });
diff --git a/packages/ui-components/test/display/natValue/test-parseAsNat.js b/packages/ui-components/test/display/natValue/test-parseAsNat.js
index 0172df9164e..6bb6677ca1c 100644
--- a/packages/ui-components/test/display/natValue/test-parseAsNat.js
+++ b/packages/ui-components/test/display/natValue/test-parseAsNat.js
@@ -45,6 +45,6 @@ test('parseAsNat ether to wei', t => {
 
 test('parseAsNat negative throws', t => {
   t.throws(() => parseAsNat('-200.00', 2), {
-    message: '(a string) must be a non-negative decimal number',
+    message: /.* must be a non-negative decimal number/,
   });
 });
diff --git a/packages/ui-components/test/display/natValue/test-roundToDecimalPlaces.js b/packages/ui-components/test/display/natValue/test-roundToDecimalPlaces.js
index 9ffa1e1a969..9002ada403a 100644
--- a/packages/ui-components/test/display/natValue/test-roundToDecimalPlaces.js
+++ b/packages/ui-components/test/display/natValue/test-roundToDecimalPlaces.js
@@ -18,14 +18,14 @@ test('roundToDecimalPlaces', t => {
 test('roundToDecimalPlaces non-string throws', t => {
   // @ts-ignore deliberate error for testing
   t.throws(() => round({}, 0), {
-    message: '(an object) must be a string',
+    message: /.* must be a string/,
   });
 });
 
 test('roundToDecimalPlaces non-num decimalPlaces throws', t => {
   // @ts-ignore deliberate error for testing
   t.throws(() => round('020', '0'), {
-    message: '(a string) must be a number',
+    message: /.* must be a number/,
   });
 });
 
diff --git a/packages/xsnap/package.json b/packages/xsnap/package.json
index 71591dd5814..b44173617d5 100644
--- a/packages/xsnap/package.json
+++ b/packages/xsnap/package.json
@@ -33,7 +33,7 @@
     "@agoric/install-ses": "^0.5.4",
     "esm": "^3.2.5",
     "glob": "^7.1.6",
-    "ses": "^0.12.3"
+    "ses": "^0.12.5"
   },
   "devDependencies": {
     "@rollup/plugin-node-resolve": "^6.1.0",
diff --git a/packages/zoe/package.json b/packages/zoe/package.json
index f71d78e77b4..78ab4990553 100644
--- a/packages/zoe/package.json
+++ b/packages/zoe/package.json
@@ -62,7 +62,7 @@
     "ava": "^3.12.1",
     "esm": "^3.2.25",
     "nyc": "^15.1.0",
-    "ses": "^0.12.3"
+    "ses": "^0.12.5"
   },
   "files": [
     "bundles/",
diff --git a/packages/zoe/test/unitTests/contractSupport/test-bondingCurves.js b/packages/zoe/test/unitTests/contractSupport/test-bondingCurves.js
index 3f90595d8f0..74e55e8f2ed 100644
--- a/packages/zoe/test/unitTests/contractSupport/test-bondingCurves.js
+++ b/packages/zoe/test/unitTests/contractSupport/test-bondingCurves.js
@@ -57,7 +57,7 @@ test('getInputPrice no reserves', t => {
     outputReserve: 0n,
     inputValue: 1n,
   };
-  const message = 'inputReserve (a bigint) must be positive';
+  const message = /inputReserve .* must be positive/;
   getInputPricethrows(t, input, message);
 });
 
@@ -127,7 +127,7 @@ test('getInputPrice bad reserve 1', t => {
     inputReserve: 43n,
     inputValue: 347n,
   };
-  const message = 'outputReserve (a bigint) must be positive';
+  const message = /outputReserve .* must be positive/;
   getInputPricethrows(t, input, message);
 });
 
@@ -137,7 +137,7 @@ test('getInputPrice bad reserve 2', t => {
     inputReserve: 0n,
     inputValue: 828n,
   };
-  const message = 'inputReserve (a bigint) must be positive';
+  const message = /inputReserve .* must be positive/;
   getInputPricethrows(t, input, message);
 });
 
@@ -147,7 +147,7 @@ test('getInputPrice zero input', t => {
     inputReserve: 320n,
     inputValue: 0n,
   };
-  const message = 'inputValue (a bigint) must be positive';
+  const message = /inputValue .* must be positive/;
   getInputPricethrows(t, input, message);
 });
 
@@ -192,7 +192,7 @@ test('getOutputPrice zero output reserve', t => {
     inputReserve: 43n,
     outputValue: 37n,
   };
-  const message = 'outputReserve (a bigint) must be positive';
+  const message = /outputReserve .* must be positive/;
   getOutputPricethrows(t, input, message);
 });
 
@@ -202,7 +202,7 @@ test('getOutputPrice zero input reserve', t => {
     inputReserve: 0n,
     outputValue: 37n,
   };
-  const message = 'inputReserve (a bigint) must be positive';
+  const message = /inputReserve .* must be positive/;
   getOutputPricethrows(t, input, message);
 });
 
@@ -212,8 +212,7 @@ test('getOutputPrice too much output', t => {
     inputReserve: 1132n,
     outputValue: 20923n,
   };
-  const message =
-    'outputReserve (a bigint) must be greater than outputValue (a bigint)';
+  const message = /outputReserve .* must be greater than outputValue .*/;
   getOutputPricethrows(t, input, message);
 });
 
@@ -223,8 +222,7 @@ test('getOutputPrice too much output 2', t => {
     inputReserve: 1132n,
     outputValue: 345n,
   };
-  const message =
-    'outputReserve (a bigint) must be greater than outputValue (a bigint)';
+  const message = /outputReserve .* must be greater than outputValue .*/;
   getOutputPricethrows(t, input, message);
 });
 
diff --git a/packages/zoe/test/unitTests/contractSupport/test-depositTo.js b/packages/zoe/test/unitTests/contractSupport/test-depositTo.js
index d0908dac285..6cc30956143 100644
--- a/packages/zoe/test/unitTests/contractSupport/test-depositTo.js
+++ b/packages/zoe/test/unitTests/contractSupport/test-depositTo.js
@@ -94,7 +94,7 @@ test(`depositToSeat - mismatched keywords`, async t => {
   await t.throwsAsync(
     () => depositToSeat(zcf, zcfSeat, { C: bucks(2) }, { D: newBucks }),
     {
-      message: `payment not found for (a string)`,
+      message: /payment not found for .*/,
     },
     'mismatched keywords',
   );
diff --git a/packages/zoe/test/unitTests/contractSupport/test-percentSupport.js b/packages/zoe/test/unitTests/contractSupport/test-percentSupport.js
index e63ac36fc03..f015a13bf14 100644
--- a/packages/zoe/test/unitTests/contractSupport/test-percentSupport.js
+++ b/packages/zoe/test/unitTests/contractSupport/test-percentSupport.js
@@ -68,9 +68,15 @@ test('ratio - complement', t => {
   amountsEqual(t, multiplyBy(moe(100000), twoThirds), moe(66666), brand);
 
   t.throws(() => oneMinus(moe(3)), {
-    message: /Parameter must be a Ratio record, but \(an object\) has "brand"/,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /Parameter must be a Ratio record, but .* has "brand"/,
+      /Parameter must be a Ratio record, but .* has .*/,
   });
   t.throws(() => oneMinus(makeRatioFromAmounts(moe(30), moe(20))), {
-    message: 'Parameter must be less than or equal to 1: (a bigint)/(a bigint)',
+    message: /Parameter must be less than or equal to 1: .*/,
   });
 });
diff --git a/packages/zoe/test/unitTests/contractSupport/test-ratio.js b/packages/zoe/test/unitTests/contractSupport/test-ratio.js
index 3f4e8f70d78..9a8c0470d94 100644
--- a/packages/zoe/test/unitTests/contractSupport/test-ratio.js
+++ b/packages/zoe/test/unitTests/contractSupport/test-ratio.js
@@ -198,10 +198,10 @@ test('ratio bad inputs', t => {
     message: 'undefined is a undefined but must be a bigint or a number',
   });
   t.throws(() => multiplyBy(37, makeRatioFromAmounts(moe(3n), moe(5n))), {
-    message: 'Expected an amount: (a number)',
+    message: /Expected an amount: .*/,
   });
   t.throws(() => divideBy(makeRatioFromAmounts(moe(3n), moe(5n)), 37), {
-    message: `Expected an amount: (an object)`,
+    message: /Expected an amount: .*/,
   });
   t.throws(() => makeRatio(3n, brand, 0n), {
     message: /No infinite ratios! Denominator was 0/,
diff --git a/packages/zoe/test/unitTests/contracts/loan/test-borrow.js b/packages/zoe/test/unitTests/contracts/loan/test-borrow.js
index a2f7d4c5880..1a8515afe82 100644
--- a/packages/zoe/test/unitTests/contracts/loan/test-borrow.js
+++ b/packages/zoe/test/unitTests/contracts/loan/test-borrow.js
@@ -153,8 +153,7 @@ test('borrow not enough collateral', async t => {
   // collateral is 0
   const { borrowSeat } = await setupBorrowFacet(0n);
   await t.throwsAsync(() => E(borrowSeat).getOfferResult(), {
-    message:
-      'The required margin is (a bigint)% but collateral only had value of (a bigint)',
+    message: /The required margin is .*% but collateral only had value of .*/,
   });
 });
 
@@ -360,8 +359,7 @@ test('getDebtNotifier with interest', async t => {
   const seat = await E(zoe).offer(closeLoanInvitation, proposal, payments);
 
   await t.throwsAsync(() => seat.getOfferResult(), {
-    message:
-      'Not enough Loan assets have been repaid.  (an object) is required, but only (an object) was repaid.',
+    message: /Not enough Loan assets have been repaid. {2}.* is required, but only .* was repaid./,
   });
 });
 
@@ -373,8 +371,7 @@ test('borrow collateral just too low', async t => {
 
   const { borrowSeat: borrowSeatBad } = await setupBorrowFacet(74n);
   await t.throwsAsync(() => E(borrowSeatBad).getOfferResult(), {
-    message:
-      'The required margin is (a bigint)% but collateral only had value of (a bigint)',
+    message: /The required margin is .*% but collateral only had value of .*/,
   });
 });
 
diff --git a/packages/zoe/test/unitTests/contracts/test-escrowToVote.js b/packages/zoe/test/unitTests/contracts/test-escrowToVote.js
index bf44f86b5e1..cef1c7f464e 100644
--- a/packages/zoe/test/unitTests/contracts/test-escrowToVote.js
+++ b/packages/zoe/test/unitTests/contracts/test-escrowToVote.js
@@ -100,7 +100,15 @@ test('zoe - escrowToVote', async t => {
     const voter = await E(seat).getOfferResult();
     await t.throwsAsync(
       () => E(voter).vote('NOT A VALID ANSWER'),
-      { message: /the answer "NOT A VALID ANSWER" was not 'YES' or 'NO'/ },
+      {
+        message:
+          // Should be able to use more informative error once SES double
+          // disclosure bug is fixed. See
+          // https://github.com/endojs/endo/pull/640
+          //
+          // /the answer "NOT A VALID ANSWER" was not 'YES' or 'NO'/
+          /the answer .* was not 'YES' or 'NO'/,
+      },
       `A vote with an invalid answer throws`,
     );
 
diff --git a/packages/zoe/test/unitTests/contracts/test-throwInOfferHandler.js b/packages/zoe/test/unitTests/contracts/test-throwInOfferHandler.js
index 099320b81b5..44806c860c0 100644
--- a/packages/zoe/test/unitTests/contracts/test-throwInOfferHandler.js
+++ b/packages/zoe/test/unitTests/contracts/test-throwInOfferHandler.js
@@ -63,7 +63,7 @@ test('throw in offerHandler', async t => {
 
   // "Rejected promise returned by test. Reason:
   // Error {
-  //   message: '"brand" not found: (an object)',
+  //   message: /"brand" not found: .*/,
   // }
   // › makeDetailedError (/Users/katesills/code/agoric-sdk/node_modules/ses/dist/ses.cjs:3437:17)
   // › fail (/Users/katesills/code/agoric-sdk/node_modules/ses/dist/ses.cjs:3582:19)
@@ -78,6 +78,12 @@ test('throw in offerHandler', async t => {
   // › src/zoeService/zoe.js:408:28"
 
   await t.throwsAsync(() => throwsInDepositToSeatResult, {
-    message: `"brand" not found: (an object)`,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"brand" not found: .*/,
+      /.* not found: .*/,
   });
 });
diff --git a/packages/zoe/test/unitTests/test-cleanProposal.js b/packages/zoe/test/unitTests/test-cleanProposal.js
index ec31e40af65..8fc976b1960 100644
--- a/packages/zoe/test/unitTests/test-cleanProposal.js
+++ b/packages/zoe/test/unitTests/test-cleanProposal.js
@@ -91,7 +91,6 @@ test('cleanProposal - wrong mathKind', t => {
   const getMathKindByBrand = _brand => MathKind.SET;
 
   t.throws(() => cleanProposal(proposal, getMathKindByBrand), {
-    message:
-      'The amount (an object) did not have the mathKind of the brand (a string)',
+    message: /The amount .* did not have the mathKind of the brand .*/,
   });
 });
diff --git a/packages/zoe/test/unitTests/test-zoe.js b/packages/zoe/test/unitTests/test-zoe.js
index 9186d1b12ab..7f5d0ff1eb0 100644
--- a/packages/zoe/test/unitTests/test-zoe.js
+++ b/packages/zoe/test/unitTests/test-zoe.js
@@ -51,7 +51,13 @@ test(`zoe.startInstance bad installation`, async t => {
   const { zoe } = setup();
   // @ts-ignore deliberate invalid arguments for testing
   await t.throwsAsync(() => E(zoe).startInstance(), {
-    message: `(an undefined) was not a valid installation`,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"\[undefined\]" was not a valid installation/,
+      /.* was not a valid installation/,
   });
 });
 
@@ -120,7 +126,13 @@ test(`zoe.startInstance - terms, issuerKeywordRecord switched`, async t => {
         { Moola: moolaKit.issuer },
       ),
     {
-      message: `keyword "something" must be ascii and must start with a capital letter.`,
+      message:
+        // Should be able to use more informative error once SES double
+        // disclosure bug is fixed. See
+        // https://github.com/endojs/endo/pull/640
+        //
+        // /keyword "something" must be ascii and must start with a capital letter./
+        /keyword .* must be ascii and must start with a capital letter./,
     },
   );
 });
@@ -136,7 +148,7 @@ test(`zoe.offer - no invitation`, async t => {
   const { zoe } = await setupZCFTest();
   // @ts-ignore deliberate invalid arguments for testing
   await t.throwsAsync(() => E(zoe).offer(), {
-    message: `A Zoe invitation is required, not (an undefined)`,
+    message: /A Zoe invitation is required, not "\[undefined\]"/,
   });
 });
 
@@ -155,7 +167,13 @@ test(`zoe.getPublicFacet - no instance`, async t => {
   const { zoe } = setup();
   // @ts-ignore deliberate invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getPublicFacet(), {
-    message: `"instance" not found: (an undefined)`,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"instance" not found: "\[undefined\]"/,
+      /.* not found: "\[undefined\]"/,
   });
 });
 
@@ -183,7 +201,13 @@ test(`zoe.getIssuers - no instance`, async t => {
   const { zoe } = setup();
   // @ts-ignore invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getIssuers(), {
-    message: `"instance" not found: (an undefined)`,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"instance" not found: "\[undefined\]"/,
+      /.* not found: "\[undefined\]"/,
   });
 });
 
@@ -211,7 +235,13 @@ test(`zoe.getBrands - no instance`, async t => {
   const { zoe } = setup();
   // @ts-ignore invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getBrands(), {
-    message: `"instance" not found: (an undefined)`,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"instance" not found: "\[undefined\]"/,
+      /.* not found: "\[undefined\]"/,
   });
 });
 
@@ -268,7 +298,13 @@ test(`zoe.getTerms - no instance`, async t => {
   const { zoe } = setup();
   // @ts-ignore invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getTerms(), {
-    message: `"instance" not found: (an undefined)`,
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"instance" not found: "\[undefined\]"/,
+      /.* not found: "\[undefined\]"/,
   });
 });
 
@@ -283,7 +319,7 @@ test(`zoe.getInstance - no invitation`, async t => {
   const { zoe } = await setupZCFTest();
   // @ts-ignore invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getInstance(), {
-    message: `A Zoe invitation is required, not (an undefined)`,
+    message: /A Zoe invitation is required, not "\[undefined\]"/,
   });
 });
 
@@ -298,7 +334,7 @@ test(`zoe.getInstallation - no invitation`, async t => {
   const { zoe } = await setupZCFTest();
   // @ts-ignore invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getInstallation(), {
-    message: `A Zoe invitation is required, not (an undefined)`,
+    message: /A Zoe invitation is required, not "\[undefined\]"/,
   });
 });
 
@@ -318,6 +354,6 @@ test(`zoe.getInvitationDetails - no invitation`, async t => {
   const { zoe } = await setupZCFTest();
   // @ts-ignore invalid arguments for testing
   await t.throwsAsync(() => E(zoe).getInvitationDetails(), {
-    message: `A Zoe invitation is required, not (an undefined)`,
+    message: /A Zoe invitation is required, not "\[undefined\]"/,
   });
 });
diff --git a/packages/zoe/test/unitTests/zcf/test-zcf.js b/packages/zoe/test/unitTests/zcf/test-zcf.js
index 37e567651a9..6b00b793bde 100644
--- a/packages/zoe/test/unitTests/zcf/test-zcf.js
+++ b/packages/zoe/test/unitTests/zcf/test-zcf.js
@@ -162,17 +162,41 @@ test(`zcf.assertUniqueKeyword`, async t => {
   const issuerKeywordRecord = { A: moolaKit.issuer, B: simoleanKit.issuer };
   const { zcf } = await setupZCFTest(issuerKeywordRecord);
   t.throws(() => zcf.assertUniqueKeyword('A'), {
-    message: 'keyword "A" must be unique',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /keyword "A" must be unique/,
+      /keyword .* must be unique/,
   });
   t.throws(() => zcf.assertUniqueKeyword('B'), {
-    message: 'keyword "B" must be unique',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /keyword "B" must be unique/,
+      /keyword .* must be unique/,
   });
   // Unique, but not a valid Keyword
   t.throws(() => zcf.assertUniqueKeyword('a'), {
-    message: 'keyword "a" must be ascii and must start with a capital letter.',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // 'keyword "a" must be ascii and must start with a capital letter.',
+      /keyword .* must be ascii and must start with a capital letter./,
   });
   t.throws(() => zcf.assertUniqueKeyword('3'), {
-    message: 'keyword "3" must be ascii and must start with a capital letter.',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // 'keyword "3" must be ascii and must start with a capital letter.',
+      /keyword .* must be ascii and must start with a capital letter./,
   });
   zcf.assertUniqueKeyword('MyKeyword');
 });
@@ -226,7 +250,13 @@ test(`zcf.saveIssuer - bad keyword`, async t => {
   await t.throwsAsync(
     async () => zcf.saveIssuer(moolaKit.issuer, 'bad keyword'),
     {
-      message: `keyword "bad keyword" must be ascii and must start with a capital letter.`,
+      message:
+        // Should be able to use more informative error once SES double
+        // disclosure bug is fixed. See
+        // https://github.com/endojs/endo/pull/640
+        //
+        // `keyword "bad keyword" must be ascii and must start with a capital letter.`,
+        /keyword .* must be ascii and must start with a capital letter./,
     },
   );
 });
@@ -238,7 +268,7 @@ test(`zcf.saveIssuer - args reversed`, async t => {
   // https://github.com/Agoric/agoric-sdk/issues/1702
   // @ts-ignore deliberate invalid arguments for testing
   await t.throwsAsync(async () => zcf.saveIssuer('A', moolaKit.issuer), {
-    message: `(an object) must be a string`,
+    message: /.* must be a string/,
   });
 });
 
@@ -283,7 +313,7 @@ test(`zcf.makeInvitation - no description`, async t => {
   const { zcf } = await setupZCFTest();
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => zcf.makeInvitation(() => {}), {
-    message: `invitations must have a description string: (an undefined)`,
+    message: /invitations must have a description string: "\[undefined\]"/,
   });
 });
 
@@ -293,7 +323,7 @@ test(`zcf.makeInvitation - non-string description`, async t => {
   // https://github.com/Agoric/agoric-sdk/issues/1704
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => zcf.makeInvitation(() => {}, { something: 'a' }), {
-    message: `invitations must have a description string: (an object)`,
+    message: /invitations must have a description string: .*/,
   });
 });
 
@@ -348,7 +378,13 @@ test(`zcf.makeZCFMint - no keyword`, async t => {
   const { zcf } = await setupZCFTest();
   // @ts-ignore deliberate invalid arguments for testing
   await t.throwsAsync(() => zcf.makeZCFMint(), {
-    message: '(an undefined) must be a string',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"\[undefined\]" must be a string/,
+      /.* must be a string/,
   });
 });
 
@@ -356,14 +392,20 @@ test(`zcf.makeZCFMint - keyword already in use`, async t => {
   const { moolaIssuer } = setup();
   const { zcf } = await setupZCFTest({ A: moolaIssuer });
   await t.throwsAsync(() => zcf.makeZCFMint('A'), {
-    message: 'Keyword (a string) already registered',
+    message: /Keyword .* already registered/,
   });
 });
 
 test(`zcf.makeZCFMint - bad keyword`, async t => {
   const { zcf } = await setupZCFTest();
   await t.throwsAsync(() => zcf.makeZCFMint('a'), {
-    message: 'keyword "a" must be ascii and must start with a capital letter.',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // 'keyword "a" must be ascii and must start with a capital letter.',
+      /keyword .* must be ascii and must start with a capital letter./,
   });
 });
 
@@ -371,8 +413,7 @@ test(`zcf.makeZCFMint - not a math kind`, async t => {
   const { zcf } = await setupZCFTest();
   // @ts-ignore deliberate invalid arguments for testing
   await t.throwsAsync(() => zcf.makeZCFMint('A', 'whatever'), {
-    message:
-      '(a string) must be MathKind.NAT or MathKind.SET. MathKind.STRING_SET is accepted but deprecated',
+    message: /.* must be MathKind.NAT or MathKind.SET. MathKind.STRING_SET is accepted but deprecated/,
   });
 });
 
@@ -421,7 +462,7 @@ test(`zcf.makeZCFMint - mintGains - no args`, async t => {
   const zcfMint = await zcf.makeZCFMint('A', MathKind.SET);
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => zcfMint.mintGains(), {
-    message: `gains (an undefined) must be an amountKeywordRecord`,
+    message: /gains "\[undefined\]" must be an amountKeywordRecord/,
   });
 });
 
@@ -445,7 +486,7 @@ test(`zcf.makeZCFMint - mintGains - no gains`, async t => {
   // https://github.com/Agoric/agoric-sdk/issues/1696
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => zcfMint.mintGains(undefined, zcfSeat), {
-    message: 'gains (an undefined) must be an amountKeywordRecord',
+    message: /gains "\[undefined\]" must be an amountKeywordRecord/,
   });
 });
 
@@ -454,7 +495,7 @@ test(`zcf.makeZCFMint - burnLosses - no args`, async t => {
   const zcfMint = await zcf.makeZCFMint('A', MathKind.SET);
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => zcfMint.burnLosses(), {
-    message: 'losses (an undefined) must be an amountKeywordRecord',
+    message: /losses "\[undefined\]" must be an amountKeywordRecord/,
   });
 });
 
@@ -464,7 +505,7 @@ test(`zcf.makeZCFMint - burnLosses - no losses`, async t => {
   const { zcfSeat } = zcf.makeEmptySeatKit();
   // @ts-ignore deliberate invalid arguments for testing
   t.throws(() => zcfMint.burnLosses(undefined, zcfSeat), {
-    message: 'losses (an undefined) must be an amountKeywordRecord',
+    message: /losses "\[undefined\]" must be an amountKeywordRecord/,
   });
 });
 
@@ -475,7 +516,7 @@ test(`zcf.makeZCFMint - mintGains - wrong brand`, async t => {
   const zcfMint = await zcf.makeZCFMint('A', MathKind.SET);
   const { zcfSeat } = zcf.makeEmptySeatKit();
   t.throws(() => zcfMint.mintGains({ Moola: moola(3) }, zcfSeat), {
-    message: `Only digital assets of brand (an object) can be minted in this call. (an object) has the wrong brand.`,
+    message: /Only digital assets of brand .* can be minted in this call. .* has the wrong brand./,
   });
 });
 
@@ -486,7 +527,7 @@ test(`zcf.makeZCFMint - burnLosses - wrong brand`, async t => {
   const zcfMint = await zcf.makeZCFMint('A', MathKind.SET);
   const { zcfSeat } = zcf.makeEmptySeatKit();
   t.throws(() => zcfMint.burnLosses({ Moola: moola(3) }, zcfSeat), {
-    message: `Only digital assets of brand (an object) can be burned in this call. (an object) has the wrong brand.`,
+    message: /Only digital assets of brand .* can be burned in this call. .* has the wrong brand./,
   });
 });
 
@@ -1200,7 +1241,7 @@ test(`zcf.reallocate 3 seats, rights NOT conserved`, async t => {
   });
 
   t.throws(() => zcf.reallocate(staging1, staging2, staging3), {
-    message: `rights were not conserved for brand (an object)`,
+    message: /rights were not conserved for brand .*/,
   });
 
   t.deepEqual(zcfSeat1.getCurrentAllocation(), {
diff --git a/packages/zoe/test/unitTests/zcf/test-zoeHelpersWZcf.js b/packages/zoe/test/unitTests/zcf/test-zoeHelpersWZcf.js
index c22049abb9a..319e905b2ee 100644
--- a/packages/zoe/test/unitTests/zcf/test-zoeHelpersWZcf.js
+++ b/packages/zoe/test/unitTests/zcf/test-zoeHelpersWZcf.js
@@ -119,7 +119,7 @@ test.failing(`zcf assertUsesNatMath - not brand`, async t => {
   // TODO: distinguish non-brands from brands
   // https://github.com/Agoric/agoric-sdk/issues/1800
   t.throws(() => assertUsesNatMath(zcf, issuer), {
-    message: /assertUsesNatMath requires a brand, not (an object)/,
+    message: /assertUsesNatMath requires a brand, not .*/,
   });
 });
 
@@ -127,7 +127,13 @@ test(`zcf assertUsesNatMath - brand not registered`, async t => {
   const { zcf } = await setupZCFTest();
   const { brand } = makeIssuerKit('gelt');
   t.throws(() => assertUsesNatMath(zcf, brand), {
-    message: '"brand" not found: (an object)',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"brand" not found: .*/,
+      /.* not found: .*/,
   });
 });
 
@@ -188,14 +194,26 @@ test(`zcf saveAllIssuers - duplicate keyword`, async t => {
   t.throws(
     () => zcf.getBrandForIssuer(pIssuer),
     {
-      message: '"issuer" not found: (an object)',
+      message:
+        // Should be able to use more informative error once SES double
+        // disclosure bug is fixed. See
+        // https://github.com/endojs/endo/pull/640
+        //
+        // /"issuer" not found: .*/,
+        /.* not found: .*/,
     },
     'issuer should not be found',
   );
 
   t.notThrows(() => assertUsesNatMath(zcf, pandaBrand), 'default');
   t.throws(() => assertUsesNatMath(zcf, pBrand), {
-    message: '"brand" not found: (an object)',
+    message:
+      // Should be able to use more informative error once SES double
+      // disclosure bug is fixed. See
+      // https://github.com/endojs/endo/pull/640
+      //
+      // /"brand" not found: .*/,
+      /.* not found: .*/,
   });
 });
 
@@ -220,28 +238,28 @@ test(`zoeHelper with zcf - assertIssuerKeywords`, async t => {
   t.throws(
     () => assertIssuerKeywords(zcf, []),
     {
-      message: 'keywords: (an object) were not as expected: (an object)',
+      message: /keywords: .* were not as expected: .*/,
     },
     'empty keywordRecord does not match',
   );
   t.throws(
     () => assertIssuerKeywords(zcf, ['A']),
     {
-      message: 'keywords: (an object) were not as expected: (an object)',
+      message: /keywords: .* were not as expected: .*/,
     },
     'missing keyword from keywordRecord does not match',
   );
   t.throws(
     () => assertIssuerKeywords(zcf, ['A', 'b']),
     {
-      message: 'keywords: (an object) were not as expected: (an object)',
+      message: /keywords: .* were not as expected: .*/,
     },
     'wrong keyword in keywordRecord does not match',
   );
   t.throws(
     () => assertIssuerKeywords(zcf, ['A', 'B', 'C']),
     {
-      message: 'keywords: (an object) were not as expected: (an object)',
+      message: /keywords: .* were not as expected: .*/,
     },
     'extra keywords in keywordRecord does not match',
   );
@@ -281,7 +299,7 @@ test(`zoeHelper with zcf - assertProposalShape`, async t => {
   t.throws(
     () => assertProposalShape(zcfSeat, { want: { C: null } }),
     {
-      message: 'actual (an object) did not match expected (an object)',
+      message: /actual .* did not match expected .*/,
     },
     'empty keywordRecord does not match',
   );
@@ -290,14 +308,14 @@ test(`zoeHelper with zcf - assertProposalShape`, async t => {
   t.throws(
     () => assertProposalShape(zcfSeat, { give: { c: null } }),
     {
-      message: 'actual (an object) did not match expected (an object)',
+      message: /actual .* did not match expected .*/,
     },
     'wrong key in keywordRecord does not match',
   );
   t.throws(
     () => assertProposalShape(zcfSeat, { exit: { onDemaind: null } }),
     {
-      message: 'actual (an object) did not match expected (an object)',
+      message: /actual .* did not match expected .*/,
     },
     'missing exit rule',
   );
@@ -514,6 +532,6 @@ test(`zcf/zoeHelper - assertProposalShape w/bad Expected`, async t => {
 
   // @ts-ignore invalid arguments for testing
   t.throws(() => assertProposalShape(zcfSeat, { give: { B: moola(3) } }), {
-    message: `The value of the expected record must be null but was (an object)`,
+    message: /The value of the expected record must be null but was .*/,
   });
 });