--- a/include/SDL_config_os2.h	Thu Mar 23 21:46:24 2006 +0000
+++ b/include/SDL_config_os2.h	Thu Mar 23 21:52:47 2006 +0000
@@ -22,6 +22,9 @@
 
 #ifndef _SDL_config_os2_h
 #define _SDL_config_os2_h
+#ifndef _SDL_config_h
+#error This file should be included from SDL_config.h - Copy SDL_config.h.default to SDL_config.h?
+#endif
 
 /* This is a set of defines to configure the SDL features */