diff --git a/lib/buffer.js b/lib/buffer.js
index ac4f61bf5d0849..5ef207eb780863 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -175,14 +175,14 @@ Buffer.from = function(value, encodingOrOffset, length) {
   if (isAnyArrayBuffer(value))
     return fromArrayBuffer(value, encodingOrOffset, length);
 
-  if (value == null)
+  if (value === null || value === undefined)
     throw new TypeError(kFromErrorMsg);
 
   if (typeof value === 'number')
     throw new TypeError('"value" argument must not be a number');
 
   const valueOf = value.valueOf && value.valueOf();
-  if (valueOf != null && valueOf !== value)
+  if (valueOf !== null && valueOf !== undefined && valueOf !== value)
     return Buffer.from(valueOf, encodingOrOffset, length);
 
   var b = fromObject(value);
@@ -292,9 +292,9 @@ function allocate(size) {
 function fromString(string, encoding) {
   var length;
   if (typeof encoding !== 'string' || encoding.length === 0) {
-    encoding = 'utf8';
     if (string.length === 0)
       return new FastBuffer();
+    encoding = 'utf8';
     length = binding.byteLengthUtf8(string);
   } else {
     length = byteLength(string, encoding, true);