diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index c390b1e..f5e0682 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -315,6 +315,9 @@
 			goto e_inval;
 		if (val < -1 || val > 0xff)
 			goto e_inval;
+		/* RFC 3542, 6.5: default traffic class of 0x0 */
+		if (val == -1)
+			val = 0;
 		np->tclass = val;
 		retv = 0;
 		break;