diff --git a/sys/netinet/icmp6.h b/sys/netinet/icmp6.h
index 6d418d6f899..7a3dbbd8dd8 100644
--- a/sys/netinet/icmp6.h
+++ b/sys/netinet/icmp6.h
@@ -32,6 +32,8 @@
 #ifndef _NETINET_ICMP6_H_
 #define	_NETINET_ICMP6_H_
 
+#define	__KAME_NETINET_ICMP6_H_INCLUDED_
 #include <netinet6/icmp6.h>
+#undef	__KAME_NETINET_ICMP6_H_INCLUDED_
 
 #endif /* !_NETINET_ICMP6_H_ */
diff --git a/sys/netinet/in.h b/sys/netinet/in.h
index b18be00afd7..adb9524339d 100644
--- a/sys/netinet/in.h
+++ b/sys/netinet/in.h
@@ -442,7 +442,9 @@ struct ip_mreq {
 }
 
 /* INET6 stuff */
+#define	__KAME_NETINET_IN_H_INCLUDED_
 #include <netinet6/in6.h>
+#undef __KAME_NETINET_IN_H_INCLUDED_
 
 #ifdef _KERNEL
 struct ifnet; struct mbuf;	/* forward declarations for Standard C */
diff --git a/sys/netinet/ip6.h b/sys/netinet/ip6.h
index a0fe4c16eb7..2c0297fd710 100644
--- a/sys/netinet/ip6.h
+++ b/sys/netinet/ip6.h
@@ -29,4 +29,6 @@
  * $FreeBSD$
  */
 
+#define	__KAME_NETINET_IP6_H_INCLUDED_
 #include <netinet6/ip6.h>
+#undef __KAME_NETINET_IP6_H_INCLUDED_
diff --git a/sys/netinet6/icmp6.h b/sys/netinet6/icmp6.h
index c67e961aaea..feb664e619a 100644
--- a/sys/netinet6/icmp6.h
+++ b/sys/netinet6/icmp6.h
@@ -67,6 +67,10 @@
 #ifndef _NETINET6_ICMPV6_H_
 #define _NETINET6_ICMPV6_H_
 
+#if !defined(_KERNEL) && !defined(__KAME_NETINET_ICMP6_H_INCLUDED_)
+#error "do not include netinet6/icmp6.h directly, include netinet/icmp6.h"
+#endif
+
 #define ICMPV6_PLD_MAXLEN	1232	/* IPV6_MMTU - sizeof(struct ip6_hdr)
 					   - sizeof(struct icmp6_hdr) */
 
diff --git a/sys/netinet6/in6.h b/sys/netinet6/in6.h
index 7ceaad44b0b..dce0da28eb8 100644
--- a/sys/netinet6/in6.h
+++ b/sys/netinet6/in6.h
@@ -66,6 +66,10 @@
 #ifndef	_NETINET6_IN6_H_
 #define	_NETINET6_IN6_H_
 
+#if !defined(_KERNEL) && !defined(__KAME_NETINET_IN_H_INCLUDED_)
+#error "do not include netinet6/in6.h directly, include netinet/in.h"
+#endif
+
 #if !defined(_XOPEN_SOURCE)
 #include <sys/queue.h>
 #endif
diff --git a/sys/netinet6/ip6.h b/sys/netinet6/ip6.h
index 9ebd51edfde..9c609e7c946 100644
--- a/sys/netinet6/ip6.h
+++ b/sys/netinet6/ip6.h
@@ -67,6 +67,12 @@
 #ifndef _NETINET6_IPV6_H_
 #define _NETINET6_IPV6_H_
 
+#if !defined(_KERNEL) && !defined(__KAME_NETINET_IP6_H_INCLUDED_)
+#if 0 /* XXX: waiting for contrib/addrtoname.c fix */
+#error "do not include netinet6/ip6.h directly, include netinet/ip6.h"
+#endif
+#endif
+
 /*
  * Definition for internet protocol version 6.
  * RFC 2460
diff --git a/usr.sbin/rtadvd/config.c b/usr.sbin/rtadvd/config.c
index 30551614e82..0e5f80d0633 100644
--- a/usr.sbin/rtadvd/config.c
+++ b/usr.sbin/rtadvd/config.c
@@ -41,9 +41,9 @@
 
 #include <netinet/in.h>
 #include <netinet/in_var.h>
-#include <netinet6/ip6.h>
+#include <netinet/ip6.h>
 #include <netinet6/ip6_var.h>
-#include <netinet6/icmp6.h>
+#include <netinet/icmp6.h>
 
 #include <arpa/inet.h>