--- a/content/canvas/src/nsCanvasRenderingContext2D.cpp
+++ b/content/canvas/src/nsCanvasRenderingContext2D.cpp
@@ -3015,17 +3015,17 @@ NS_IMETHODIMP
 nsCanvasRenderingContext2D::DrawImage(nsIDOMElement *imgElt, float a1,
                                       float a2, float a3, float a4, float a5,
                                       float a6, float a7, float a8,
                                       PRUint8 optional_argc)
 {
     NS_ENSURE_ARG(imgElt);
 
     nsresult rv;
-    gfxRect dirty;
+    gfxRect dirty(0.0, 0.0, 0.0, 0.0);
 
     double sx,sy,sw,sh;
     double dx,dy,dw,dh;
 
     gfxMatrix matrix;
     nsRefPtr<gfxPattern> pattern;
     nsRefPtr<gfxPath> path;