diff --git a/sys/netinet/in_gif.h b/sys/netinet/in_gif.h
index dcba361b56b3..39d1aba7504b 100644
--- a/sys/netinet/in_gif.h
+++ b/sys/netinet/in_gif.h
@@ -36,7 +36,12 @@
 
 extern int ip_gif_ttl;
 
-void in_gif_input __P((struct mbuf *, int off, int proto));
-int in_gif_output __P((struct ifnet *, int, struct mbuf *, struct rtentry *));
+struct	mbuf;
+struct	ifnet;
+struct	rtentry;
+
+void	in_gif_input __P((struct mbuf *, int off, int proto));
+int	in_gif_output __P((struct ifnet *, int, struct mbuf *,
+			   struct rtentry *));
 
 #endif /*_NETINET_IN_GIF_H_*/
diff --git a/sys/netinet6/in6_gif.h b/sys/netinet6/in6_gif.h
index 7d06c3c4cba9..65d76357582c 100644
--- a/sys/netinet6/in6_gif.h
+++ b/sys/netinet6/in6_gif.h
@@ -34,7 +34,12 @@
 
 #define	GIF_HLIM	30
 
-int in6_gif_input __P((struct mbuf **, int *, int));
-int in6_gif_output __P((struct ifnet *, int, struct mbuf *, struct rtentry *));
+struct	mbuf;
+struct	ifnet;
+struct	rtentry;
+
+int	in6_gif_input __P((struct mbuf **, int *, int));
+int	in6_gif_output __P((struct ifnet *, int, struct mbuf *,
+			    struct rtentry *));
 
 #endif /*_NETINET6_IN6_GIF_H_*/
diff --git a/sys/netinet6/ip6protosw.h b/sys/netinet6/ip6protosw.h
index bf3e4dc83f2c..1e1c3c2fdd04 100644
--- a/sys/netinet6/ip6protosw.h
+++ b/sys/netinet6/ip6protosw.h
@@ -77,6 +77,7 @@
 struct	mbuf;
 struct	sockaddr;
 struct	socket;
+struct	sockopt;
 struct	domain;
 struct	proc;
 struct	ip6_hdr;