diff --git a/lib/context2d.js b/lib/context2d.js
index 882ed2e..4161050 100644
--- a/lib/context2d.js
+++ b/lib/context2d.js
@@ -483,6 +483,5 @@ Context2d.prototype.createImageData = function(width, height){
     height = width.height;
     width = width.width;
   }
-  var arr = new PixelArray(width, height);
-  return new ImageData(arr);
+  return new ImageData(new PixelArray(width, height));
 };
\ No newline at end of file
diff --git a/src/CanvasGradient.cc b/src/CanvasGradient.cc
index 5419cc2..cf99585 100644
--- a/src/CanvasGradient.cc
+++ b/src/CanvasGradient.cc
@@ -36,8 +36,6 @@ Handle<Value>
 Gradient::New(const Arguments &args) {
   HandleScope scope;
 
-  // TODO: separate concerns / validate args
-
   // Linear
   if (4 == args.Length()) {
     Gradient *grad = new Gradient(
diff --git a/src/ImageData.cc b/src/ImageData.cc
index 08bed4f..0a814f9 100644
--- a/src/ImageData.cc
+++ b/src/ImageData.cc
@@ -36,8 +36,12 @@ ImageData::Initialize(Handle<Object> target) {
 Handle<Value>
 ImageData::New(const Arguments &args) {
   HandleScope scope;
-  // TODO: arg assertions
-  PixelArray *arr = ObjectWrap::Unwrap<PixelArray>(args[0]->ToObject());
+  Local<Object> obj = args[0]->ToObject();
+
+  if (!PixelArray::constructor->HasInstance(obj))
+    return ThrowException(Exception::TypeError(String::New("CanvasPixelArray expected")));
+
+  PixelArray *arr = ObjectWrap::Unwrap<PixelArray>(obj);
   ImageData *imageData = new ImageData(arr);
   args.This()->Set(String::NewSymbol("data"), args[0]);
   imageData->Wrap(args.This());