diff --git c/pTk/mTk/xlib/X11/X.h w/pTk/mTk/xlib/X11/X.h
index 95db07f..a1cf10c 100644
--- c/pTk/mTk/xlib/X11/X.h
+++ w/pTk/mTk/xlib/X11/X.h
@@ -40,7 +40,7 @@ SOFTWARE.
 
/* Resources */
 
-#ifdef _WIN64</code>
+#if defined(_WIN64) && defined(_MSC_VER)
typedef __int64 XID;
#else
typedef unsigned long XID;