This is related to 36ffc47b6033, which fixes bug 2508.
@@ -52,7 +52,9 @@ struct SDL_SysWMinfo;
#else
#if defined(SDL_VIDEO_DRIVER_WINDOWS)
+#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
+#endif
#include <windows.h>
#endif