diff --git a/package-lock.json b/package-lock.json
index 3d6c4c7..6f250d4 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,9 +11,11 @@
       "dependencies": {
         "@solana/web3.js": "^1.30.2",
         "assert": "^2.0.0",
+        "big-integer": "^1.6.51",
         "buffer": "^6.0.1"
       },
       "devDependencies": {
+        "@types/big-integer": "^0.0.31",
         "@types/jest": "^26.0.23",
         "jest": "^27.3.1",
         "prettier": "^2.3.0",
@@ -1264,6 +1266,16 @@
         "@babel/types": "^7.3.0"
       }
     },
+    "node_modules/@types/big-integer": {
+      "version": "0.0.31",
+      "resolved": "https://registry.npmjs.org/@types/big-integer/-/big-integer-0.0.31.tgz",
+      "integrity": "sha512-nYrYenHwC07vTBXoQ8jUUi6sednNYHGQxh0ecvfWm46n3djgxxbe7AZIJVaGjzQaEQVEcH6KmB6VMt//vAP0AA==",
+      "deprecated": "This is a stub types definition for BigInteger.js (https://github.com/peterolson/BigInteger.js). BigInteger.js provides its own type definitions, so you don't need @types/big-integer installed!",
+      "dev": true,
+      "dependencies": {
+        "big-integer": "*"
+      }
+    },
     "node_modules/@types/bn.js": {
       "version": "4.11.6",
       "resolved": "https://registry.npmjs.org/@types/bn.js/-/bn.js-4.11.6.tgz",
@@ -1696,6 +1708,14 @@
         }
       ]
     },
+    "node_modules/big-integer": {
+      "version": "1.6.51",
+      "resolved": "https://registry.npmjs.org/big-integer/-/big-integer-1.6.51.tgz",
+      "integrity": "sha512-GPEid2Y9QU1Exl1rpO9B2IPJGHPSupF5GnVIP0blYvNOMer2bTvSWs1jGOUg04hTmu67nmLsQ9TBo1puaotBHg==",
+      "engines": {
+        "node": ">=0.6"
+      }
+    },
     "node_modules/bn.js": {
       "version": "5.2.0",
       "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-5.2.0.tgz",
@@ -7336,6 +7356,15 @@
         "@babel/types": "^7.3.0"
       }
     },
+    "@types/big-integer": {
+      "version": "0.0.31",
+      "resolved": "https://registry.npmjs.org/@types/big-integer/-/big-integer-0.0.31.tgz",
+      "integrity": "sha512-nYrYenHwC07vTBXoQ8jUUi6sednNYHGQxh0ecvfWm46n3djgxxbe7AZIJVaGjzQaEQVEcH6KmB6VMt//vAP0AA==",
+      "dev": true,
+      "requires": {
+        "big-integer": "*"
+      }
+    },
     "@types/bn.js": {
       "version": "4.11.6",
       "resolved": "https://registry.npmjs.org/@types/bn.js/-/bn.js-4.11.6.tgz",
@@ -7691,6 +7720,11 @@
       "resolved": "https://registry.npmjs.org/base64-js/-/base64-js-1.5.1.tgz",
       "integrity": "sha512-AKpaYlHn8t4SVbOHCy+b5+KKgvR4vrsD8vbvrbiQJps7fKDTkjkDry6ji0rUJjC0kzbNePLwzxq8iypo41qeWA=="
     },
+    "big-integer": {
+      "version": "1.6.51",
+      "resolved": "https://registry.npmjs.org/big-integer/-/big-integer-1.6.51.tgz",
+      "integrity": "sha512-GPEid2Y9QU1Exl1rpO9B2IPJGHPSupF5GnVIP0blYvNOMer2bTvSWs1jGOUg04hTmu67nmLsQ9TBo1puaotBHg=="
+    },
     "bn.js": {
       "version": "5.2.0",
       "resolved": "https://registry.npmjs.org/bn.js/-/bn.js-5.2.0.tgz",
diff --git a/package.json b/package.json
index 4c36fd5..4acd6d6 100644
--- a/package.json
+++ b/package.json
@@ -28,6 +28,7 @@
   ],
   "license": "Apache-2.0",
   "devDependencies": {
+    "@types/big-integer": "^0.0.31",
     "@types/jest": "^26.0.23",
     "jest": "^27.3.1",
     "prettier": "^2.3.0",
@@ -39,6 +40,7 @@
   "dependencies": {
     "@solana/web3.js": "^1.30.2",
     "assert": "^2.0.0",
+    "big-integer": "^1.6.51",
     "buffer": "^6.0.1"
   }
 }
diff --git a/src/readBig.ts b/src/readBig.ts
index 5ec754f..581a9b6 100644
--- a/src/readBig.ts
+++ b/src/readBig.ts
@@ -1,4 +1,5 @@
 import { Buffer } from 'buffer'
+import BigInt from 'big-integer'
 
 // https://github.com/nodejs/node/blob/v14.17.0/lib/internal/errors.js#L758
 const ERR_BUFFER_OUT_OF_BOUNDS = () => new Error('Attempt to access memory outside buffer bounds')
@@ -36,10 +37,8 @@ export function readBigInt64LE(buffer: Buffer, offset = 0): bigint {
   if (first === undefined || last === undefined) boundsError(offset, buffer.length - 8)
   // tslint:disable-next-line:no-bitwise
   const val = buffer[offset + 4] + buffer[offset + 5] * 2 ** 8 + buffer[offset + 6] * 2 ** 16 + (last << 24) // Overflow
-  return (
-    (BigInt(val) << BigInt(32)) + // tslint:disable-line:no-bitwise
-    BigInt(first + buffer[++offset] * 2 ** 8 + buffer[++offset] * 2 ** 16 + buffer[++offset] * 2 ** 24)
-  )
+  const result = BigInt(val).shiftLeft(32).add(BigInt(first + buffer[++offset] * 2 ** 8 + buffer[++offset] * 2 ** 16 + buffer[++offset] * 2 ** 24))
+  return result;
 }
 
 // https://github.com/nodejs/node/blob/v14.17.0/lib/internal/buffer.js#L89-L107
@@ -53,5 +52,5 @@ export function readBigUInt64LE(buffer: Buffer, offset = 0): bigint {
 
   const hi = buffer[++offset] + buffer[++offset] * 2 ** 8 + buffer[++offset] * 2 ** 16 + last * 2 ** 24
 
-  return BigInt(lo) + (BigInt(hi) << BigInt(32)) // tslint:disable-line:no-bitwise
+  return BigInt(hi).shiftLeft(32).add(lo) // tslint:disable-line:no-bitwise
 }
diff --git a/tsconfig.json b/tsconfig.json
index e305280..e5b2280 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,6 +4,7 @@
     "module": "commonjs",
     "declaration": true,
     "outDir": "./lib",
+    "esModuleInterop": true,
     "strict": true
   },
   "include": ["src"],