diff --git a/include/xkbrules.h b/include/xkbrules.h
index 0203984fe..8832c01e2 100644
--- a/include/xkbrules.h
+++ b/include/xkbrules.h
@@ -107,6 +107,7 @@ extern _X_EXPORT void XkbRF_Free(XkbRF_RulesPtr /* rules */ ,
 /***====================================================================***/
 
 #define	_XKB_RF_NAMES_PROP_ATOM		"_XKB_RULES_NAMES"
+#define	_XKB_RF_NAMES_PROP_MAXLEN	1024
 
 _XFUNCPROTOEND
 #endif                          /* _XKBRULES_H_ */