diff --git a/net/netfilter/xt_DSCP.c b/net/netfilter/xt_DSCP.c
index fd7500e..9951e7f 100644
--- a/net/netfilter/xt_DSCP.c
+++ b/net/netfilter/xt_DSCP.c
@@ -128,7 +128,7 @@
 	u_int8_t orig, nv;
 
 	orig = ipv4_get_dsfield(iph);
-	nv   = (orig & info->tos_mask) ^ info->tos_value;
+	nv   = (orig & ~info->tos_mask) ^ info->tos_value;
 
 	if (orig != nv) {
 		if (!skb_make_writable(skb, sizeof(struct iphdr)))