diff --git a/include/wx/app.h b/include/wx/app.h
index cb327df858..ab9e88a562 100644
--- a/include/wx/app.h
+++ b/include/wx/app.h
@@ -384,7 +384,7 @@ public:
     // this includes <windows.h> which is a bad thing because it prevents
     // wxWindows to work with MFC, so for now I'm making this change for
     // mingw/cygwin only (these don't work with MFC yet). GRG Mar/2000
-    #ifdef(__GNUWIN32__)
+    #if defined(__GNUWIN32__)
         #include <windows.h>
         #include "wx/msw/winundef.h"