diff --git a/src/msw/frame.cpp b/src/msw/frame.cpp
index e99831a461..0a453aba9a 100644
--- a/src/msw/frame.cpp
+++ b/src/msw/frame.cpp
@@ -926,7 +926,7 @@ void wxFrameMSW::IconizeChildFrames(bool bIconize)
 
         // the child MDI frames are a special case and should not be touched by
         // the parent frame - instead, they are managed by the user
-        wxFrameMSW *frame = wxDynamicCast(win, wxFrameMSW);
+        wxFrameMSW *frame = wxDynamicCast(win, wxFrame);
         if ( frame
 #if wxUSE_MDI_ARCHITECTURE
                 && !wxDynamicCast(frame, wxMDIChildFrame)