diff --git a/content/html/content/src/nsHTMLCanvasElement.cpp b/content/html/content/src/nsHTMLCanvasElement.cpp
index 21fa160d99be..15637bf5d18f 100644
--- a/content/html/content/src/nsHTMLCanvasElement.cpp
+++ b/content/html/content/src/nsHTMLCanvasElement.cpp
@@ -709,6 +709,8 @@ nsHTMLCanvasElement::InvalidateCanvasContent(const gfxRect* damageRect)
       // then make it a nsRect
       invalRect = nsRect(realRect.X(), realRect.Y(),
                          realRect.Width(), realRect.Height());
+
+      invalRect = invalRect.Intersect(nsRect(nsPoint(0,0), contentArea.Size()));
     }
   } else {
     invalRect = nsRect(nsPoint(0, 0), contentArea.Size());