diff --git a/XI.h b/XI.h
index ae52292..0bfefcc 100644
--- a/XI.h
+++ b/XI.h
@@ -50,9 +50,10 @@ SOFTWARE.
 /* Definitions used by the server, library and client */
 
 #ifndef _XI_H_
-
 #define _XI_H_
 
+#include <X11/X.h> /* CARD32 */
+
 #define sz_xGetExtensionVersionReq		8
 #define sz_xGetExtensionVersionReply		32
 #define sz_xListInputDevicesReq			4