diff --git a/sys/sys/msg.h b/sys/sys/msg.h
index 4a170a2dc401..d34a6d707d69 100644
--- a/sys/sys/msg.h
+++ b/sys/sys/msg.h
@@ -23,6 +23,8 @@
 #ifndef _SYS_MSG_H_
 #define _SYS_MSG_H_
 
+#include <sys/cdefs.h>
+#include <sys/_types.h>
 #include <sys/ipc.h>
 
 /*
@@ -32,15 +34,39 @@
 
 #define MSG_NOERROR	010000		/* don't complain about too long msgs */
 
+typedef	unsigned long	msglen_t;
+typedef	unsigned long	msgqnum_t;
+
+#ifndef _PID_T_DECLARED
+typedef	__pid_t		pid_t;
+#define	_PID_T_DECLARED
+#endif
+
+#ifndef _TIME_T_DECLARED
+typedef	__time_t	time_t;
+#define	_TIME_T_DECLARED
+#endif
+
+#ifndef _SIZE_T_DECLARED
+typedef	__size_t	size_t;
+#define	_SIZE_T_DECLARED
+#endif
+
+#ifndef _SSIZE_T_DECLARED
+typedef	__ssize_t	ssize_t;
+#define	_SSIZE_T_DECLARED
+#endif
+
+/* XXX namespace pollution. */
 struct msg;
 
 struct msqid_ds {
 	struct	ipc_perm msg_perm;	/* msg queue permission bits */
 	struct	msg *msg_first;	/* first message in the queue */
 	struct	msg *msg_last;	/* last message in the queue */
-	u_long	msg_cbytes;	/* number of bytes in use on the queue */
-	u_long	msg_qnum;	/* number of msgs in the queue */
-	u_long	msg_qbytes;	/* max # of bytes on the queue */
+	msglen_t msg_cbytes;	/* number of bytes in use on the queue */
+	msgqnum_t msg_qnum;	/* number of msgs in the queue */
+	msglen_t msg_qbytes;	/* max # of bytes on the queue */
 	pid_t	msg_lspid;	/* pid of last msgsnd() */
 	pid_t	msg_lrpid;	/* pid of last msgrcv() */
 	time_t	msg_stime;	/* time of last msgsnd() */
@@ -52,6 +78,7 @@ struct msqid_ds {
 	long	msg_pad4[4];
 };
 
+#if __BSD_VISIBLE
 /*
  * Structure describing a message.  The SVID doesn't suggest any
  * particular name for this structure.  There is a reference in the
@@ -66,6 +93,7 @@ struct mymsg {
 	long	mtype;		/* message type (+ve integer) */
 	char	mtext[1];	/* message body */
 };
+#endif
 
 #ifdef _KERNEL
 
@@ -92,15 +120,18 @@ extern struct msginfo	msginfo;
 
 #ifndef _KERNEL
 
-#include <sys/cdefs.h>
-
 __BEGIN_DECLS
-int msgsys(int, ...);
 int msgctl(int, int, struct msqid_ds *);
 int msgget(key_t, int);
+/* XXX return value should be ssize_t. */
+int msgrcv(int, void *, size_t, long, int);
+/* XXX second parameter missing const type-qualifier. */
 int msgsnd(int, void *, size_t, int);
-int msgrcv(int, void*, size_t, long, int);
+#if __BSD_VISIBLE
+int msgsys(int, ...);
+#endif
 __END_DECLS
+
 #endif
 
 #endif /* !_SYS_MSG_H_ */