diff --git a/clatd.h b/clatd.h
index 6907829..75ffea3 100644
--- a/clatd.h
+++ b/clatd.h
@@ -41,7 +41,7 @@
 void configure_tun_ip(const struct tun_data *tunnel, const char *v4_addr, int mtu);
 void set_capability(uint64_t target_cap);
 void drop_root_and_caps();
-void open_sockets(struct tun_data *tunnel);
+void open_sockets(struct tun_data *tunnel, uint32_t mark);
 int ipv6_address_changed(const char *interface);
 int configure_clat_ipv6_address(const struct tun_data *tunnel, const char *interface,
                                 const char *src_addr);