diff --git a/sys/netinet/udp_var.h b/sys/netinet/udp_var.h
index 7e7cfba2eeb..6e5abd05c21 100644
--- a/sys/netinet/udp_var.h
+++ b/sys/netinet/udp_var.h
@@ -51,6 +51,9 @@ struct udpiphdr {
 #define	ui_ulen		ui_u.uh_ulen
 #define	ui_sum		ui_u.uh_sum
 
+struct inpcb;
+struct mbuf;
+
 typedef void(*udp_tun_func_t)(struct mbuf *, int off, struct inpcb *);
 
 /*