diff --git a/src/raster/image_iterator.h b/src/raster/image_iterator.h
index ce52e2607..0325b4628 100644
--- a/src/raster/image_iterator.h
+++ b/src/raster/image_iterator.h
@@ -80,6 +80,7 @@ namespace raster {
 #endif
     {
       ASSERT(bounds.contains(gfx::Point(x, y)));
+      ASSERT(image->getBounds().contains(bounds));
     }
 
     ImageIteratorT& operator=(const ImageIteratorT& other) {