diff --git a/index.js b/index.js
index d1275e6..089aefb 100644
--- a/index.js
+++ b/index.js
@@ -63,7 +63,7 @@ function bufferToBase64(arr) {
 function binaryStringToBuffer(binstr) {
   var buf;
 
-  if ('undefined' === typeof Uint8Array) {
+  if ('undefined' !== typeof Uint8Array) {
     buf = new Uint8Array(binstr.length);
   } else {
     buf = [];