diff --git a/widget/src/gtk2/nsWindow.cpp b/widget/src/gtk2/nsWindow.cpp
index 6addb6e8b6e5..1ae79f1c7450 100644
--- a/widget/src/gtk2/nsWindow.cpp
+++ b/widget/src/gtk2/nsWindow.cpp
@@ -495,7 +495,7 @@ nsWindow::InvalidateRegion(const nsIRegion* aRegion,
 			   PRBool           aIsSynchronous)
 {
   GdkRegion *region = nsnull;
-  aRegion->GetNativeRegion((void *)region);
+  aRegion->GetNativeRegion((void *&)region);
 
   if (region) {
     GdkRectangle rect;