diff --git a/include/win32/vc/config.h b/include/win32/vc/config.h
index 9bae7cd..c4ebb7d 100644
--- a/include/win32/vc/config.h
+++ b/include/win32/vc/config.h
@@ -261,7 +261,7 @@
 #define GLOBAL_CFG_FILE ".\\qforge.cfg"
 
 /* Posix, needed for limits.h and Unix stuffs to work right */
-#undef _POSIX_
+#define _POSIX_
 
 /* Define if we've scitech MGL library and mgraph.h */
 #define HAVE_MGRAPH_H 1