--- a/windowing/windowserver/nga/SERVER/drawresource.cpp	Tue Apr 20 16:38:10 2010 +0100
+++ b/windowing/windowserver/nga/SERVER/drawresource.cpp	Fri Apr 23 14:57:14 2010 +0100
@@ -45,6 +45,7 @@
 		User::Leave(KErrArgument);
 		}
 	MWsScreen* pOI=screen;
+	WS_ASSERT_ALWAYS(pOI, EWsPanicNoScreen);
 	CWsDrawableSource::iDrawResource = pOI->ObjectInterface<MWsDrawableSourceProvider>();
 	if (!iDrawResource)
 		{