diff --git a/lib/storage/file.js b/lib/storage/file.js
index d5f20e7531f..fe3502589f6 100644
--- a/lib/storage/file.js
+++ b/lib/storage/file.js
@@ -1391,7 +1391,7 @@ File.prototype.startResumableUpload_ = function(stream, metadata) {
       // byte of incoming data.
       if (bytesWritten === 0) {
         var cachedFirstChunk = config && config.firstChunk;
-        var firstChunk = chunk.slice(0, 16);
+        var firstChunk = chunk.slice(0, 16).valueOf();
 
         if (!cachedFirstChunk) {
           // This is a new upload. Cache the first chunk.