--- a/gfx/thebes/gfxASurface.cpp
+++ b/gfx/thebes/gfxASurface.cpp
@@ -483,16 +483,23 @@ void
 gfxASurface::MovePixels(const nsIntRect& aSourceRect,
                         const nsIntPoint& aDestTopLeft)
 {
     // Assume the backend can't handle self copying well and allocate
     // a temporary surface instead.
     nsRefPtr<gfxASurface> tmp = 
       CreateSimilarSurface(GetContentType(), 
                            gfxIntSize(aSourceRect.width, aSourceRect.height));
+    // CreateSimilarSurface can return nsnull if the current surface is
+    // in an error state. This isn't good, but its better to carry
+    // on with the error surface instead of crashing.
+    NS_ASSERTION(tmp, "Must have temporary surface to move pixels!");
+    if (!tmp) {
+        return;
+    }
     nsRefPtr<gfxContext> ctx = new gfxContext(tmp);
     ctx->SetOperator(gfxContext::OPERATOR_SOURCE);
     ctx->SetSource(this, gfxPoint(-aSourceRect.x, -aSourceRect.y));
     ctx->Paint();
 
     ctx = new gfxContext(this);
     ctx->SetOperator(gfxContext::OPERATOR_SOURCE);
     ctx->SetSource(tmp, gfxPoint(aDestTopLeft.x, aDestTopLeft.y));