For Windows, need to add #include <windows.h>.
diff --git a/Python/importdl.h b/Python/importdl.h
index 5c729a8..0556313 100644
--- a/Python/importdl.h
+++ b/Python/importdl.h
@@ -64,6 +64,7 @@
 #define MAXSUFFIXSIZE 12
 
 #ifdef MS_WINDOWS
+#include <windows.h>
 typedef FARPROC dl_funcptr;
 #else
 #ifdef PYOS_OS2