diff --git a/lib/buffer.js b/lib/buffer.js
index 0a8724bda48e48..cb93d7e2488f3b 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -463,7 +463,7 @@ function slowToString(encoding, start, end) {
   if (end <= start)
     return '';
 
-  if (!encoding) encoding = 'utf8';
+  if (encoding === undefined) encoding = 'utf8';
 
   while (true) {
     switch (encoding) {
diff --git a/test/parallel/test-buffer-tostring-range.js b/test/parallel/test-buffer-tostring-range.js
index c7ab356e4661ff..a550906912a480 100644
--- a/test/parallel/test-buffer-tostring-range.js
+++ b/test/parallel/test-buffer-tostring-range.js
@@ -82,3 +82,11 @@ assert.strictEqual(rangeBuffer.toString('ascii', 0, true), 'a');
 assert.strictEqual(rangeBuffer.toString({toString: function() {
   return 'ascii';
 }}), 'abc');
+
+// try toString() with 0 and null as the encoding
+assert.throws(() => {
+  rangeBuffer.toString(0, 1, 2);
+}, /^TypeError: Unknown encoding: 0$/);
+assert.throws(() => {
+  rangeBuffer.toString(null, 1, 2);
+}, /^TypeError: Unknown encoding: null$/);