diff --git a/lib/imagedata.js b/lib/imagedata.js
index a2351ea6..8f405b60 100644
--- a/lib/imagedata.js
+++ b/lib/imagedata.js
@@ -1,5 +1,5 @@
 function ImageData(width, height) {
-  if (width instanceof ImageData) {
+  if (width && width instanceof Object) {
     this.width = width.width;
     this.height = width.height;
     this.data = width.data;