diff --git a/lib/fs.js b/lib/fs.js
index 77bcbac61a5eca..472d03cc75414c 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -1099,7 +1099,9 @@ function writeAll(fd, buffer, offset, length, position, callback) {
       } else {
         offset += written;
         length -= written;
-        position += written;
+        if (position !== null) {
+          position += written;
+        }
         writeAll(fd, buffer, offset, length, position, callback);
       }
     }
@@ -1148,13 +1150,17 @@ fs.writeFileSync = function(path, data, options) {
   if (!(data instanceof Buffer)) {
     data = new Buffer('' + data, options.encoding || 'utf8');
   }
-  var written = 0;
+  var offset = 0;
   var length = data.length;
   var position = /a/.test(flag) ? null : 0;
   try {
-    while (written < length) {
-      written += fs.writeSync(fd, data, written, length - written, position);
-      position += written;
+    while (length > 0) {
+      var written = fs.writeSync(fd, data, offset, length, position);
+      offset += written;
+      length -= written;
+      if (position !== null) {
+        position += written;
+      }
     }
   } finally {
     fs.closeSync(fd);