diff --git a/src/filesystem/implementation.js b/src/filesystem/implementation.js
index 6f69631..b4c65f4 100644
--- a/src/filesystem/implementation.js
+++ b/src/filesystem/implementation.js
@@ -1875,7 +1875,7 @@ function appendFile(fs, context, path, data, options, callback) {
   if(typeof data === 'number') {
     data = '' + data;
   }
-  if(typeof data === 'string' && (options.encoding == null || options.encoding === 'utf8')) {
+  if(typeof data === 'string' && (options.encoding === null || options.encoding === 'utf8')) {
     data = Encoding.encode(data);
   }