diff --git a/sys/netinet/fil.c b/sys/netinet/fil.c
index 95611422e85..3a5444ade0b 100644
--- a/sys/netinet/fil.c
+++ b/sys/netinet/fil.c
@@ -87,6 +87,8 @@ static const char rcsid[] = "@(#)$FreeBSD$";
 #endif
 #include "netinet/ipl.h"
 
+#include <machine/in_cksum.h>
+
 #ifndef	_KERNEL
 # include "ipf.h"
 # include "ipt.h"
diff --git a/sys/netinet/ip_fil.c b/sys/netinet/ip_fil.c
index 8216537dbbf..08117a783ed 100644
--- a/sys/netinet/ip_fil.c
+++ b/sys/netinet/ip_fil.c
@@ -114,6 +114,7 @@ static const char rcsid[] = "@(#)$FreeBSD$";
 extern	int	ip_optcopy __P((struct ip *, struct ip *));
 #endif
 
+#include <machine/in_cksum.h>
 
 extern	struct	protosw	inetsw[];
 
diff --git a/sys/netinet6/ipsec.c b/sys/netinet6/ipsec.c
index d9cf133da76..a72fb6a96cd 100644
--- a/sys/netinet6/ipsec.c
+++ b/sys/netinet6/ipsec.c
@@ -97,6 +97,8 @@
 #define	KEYDEBUG(lev,arg)
 #endif
 
+#include <machine/in_cksum.h>
+
 struct ipsecstat ipsecstat;
 int ip4_inbound_call_ike = 0;
 int ip4_ah_cleartos = 1;