diff --git a/include/common/compat.h b/include/common/compat.h
index a0764b1..48ea1f7 100644
--- a/include/common/compat.h
+++ b/include/common/compat.h
@@ -129,6 +129,14 @@
 #endif
 #endif
 
+/* If IPv6 is supported, define IN6_IS_ADDR_V4MAPPED() if missing. */
+#if defined(IPV6_TCLASS) && !defined(IN6_IS_ADDR_V4MAPPED)
+#define IN6_IS_ADDR_V4MAPPED(a) \
+((((const uint32_t *) (a))[0] == 0) \
+&& (((const uint32_t *) (a))[1] == 0) \
+&& (((const uint32_t *) (a))[2] == htonl (0xffff)))
+#endif
+
 #if defined(__dietlibc__)
 #include <strings.h>
 #endif
diff --git a/src/proto_http.c b/src/proto_http.c
index d21bd8a..8c336e6 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -3158,6 +3158,26 @@
 	return 1;
 }
 
+/* Sets the TOS header in IPv4 and the traffic class header in IPv6 packets
+ * (as per RFC3260 #4 and BCP37 #4.2 and #5.2).
+ */
+static inline void inet_set_tos(int fd, struct sockaddr_storage from, int tos)
+{
+#ifdef IP_TOS
+	if (from.ss_family == AF_INET)
+		setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
+#endif
+#ifdef IPV6_TCLASS
+	if (from.ss_family == AF_INET6) {
+		if (IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)&from)->sin6_addr))
+			/* v4-mapped addresses need IP_TOS */
+			setsockopt(fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos));
+		else
+			setsockopt(fd, IPPROTO_IPV6, IPV6_TCLASS, &tos, sizeof(tos));
+	}
+#endif
+}
+
 /* Executes the http-request rules <rules> for session <s>, proxy <px> and
  * transaction <txn>. Returns the first rule that prevents further processing
  * of the request (auth, deny, ...) or NULL if it executed all rules or stopped
@@ -3212,10 +3232,7 @@
 			break;
 
 		case HTTP_REQ_ACT_SET_TOS:
-#ifdef IP_TOS
-			if (s->req->prod->conn->addr.from.ss_family == AF_INET)
-				setsockopt(s->req->prod->conn->t.sock.fd, IPPROTO_IP, IP_TOS, &rule->arg.tos, sizeof(rule->arg.tos));
-#endif
+			inet_set_tos(s->req->prod->conn->t.sock.fd, s->req->prod->conn->addr.from, rule->arg.tos);
 			break;
 
 		case HTTP_REQ_ACT_SET_MARK:
@@ -3298,10 +3315,7 @@
 			break;
 
 		case HTTP_RES_ACT_SET_TOS:
-#ifdef IP_TOS
-			if (s->req->prod->conn->addr.from.ss_family == AF_INET)
-				setsockopt(s->req->prod->conn->t.sock.fd, IPPROTO_IP, IP_TOS, &rule->arg.tos, sizeof(rule->arg.tos));
-#endif
+			inet_set_tos(s->req->prod->conn->t.sock.fd, s->req->prod->conn->addr.from, rule->arg.tos);
 			break;
 
 		case HTTP_RES_ACT_SET_MARK: