diff --git a/xt_dscp.h b/xt_dscp.h
index 648e0b3..210a23a 100644
--- a/include/uapi/linux/netfilter/xt_dscp.h
+++ b/include/uapi/linux/netfilter/xt_dscp.h
@@ -13,6 +13,8 @@
 #include <linux/netfilter/xt_dscp.h>
 #include <linux/types.h>
 
+#define XT_DSCP_MASK 0xfc
+
 /* target info */
 struct xt_DSCP_info {
 	__u8 dscp;
