diff --git a/layout/generic/nsCanvasFrame.cpp b/layout/generic/nsCanvasFrame.cpp
index b9bd9e70f5ea..8146c506c90b 100644
--- a/layout/generic/nsCanvasFrame.cpp
+++ b/layout/generic/nsCanvasFrame.cpp
@@ -292,6 +292,10 @@ public:
   nsDisplayCanvasFocus(nsCanvasFrame *aFrame)
     : nsDisplayItem(aFrame)
   {
+    MOZ_COUNT_CTOR(nsDisplayCanvasFocus);
+  }
+  virtual ~nsDisplayCanvasFocus() {
+    MOZ_COUNT_DTOR(nsDisplayCanvasFocus);
   }
 
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder)