diff --git a/sys/compat/freebsd32/freebsd32_ipc.h b/sys/compat/freebsd32/freebsd32_ipc.h
index 320a63f0c2dd..1f457f8f678f 100644
--- a/sys/compat/freebsd32/freebsd32_ipc.h
+++ b/sys/compat/freebsd32/freebsd32_ipc.h
@@ -72,7 +72,7 @@ struct shmid_ds32 {
 	int32_t		shm_segsz;
 	pid_t		shm_lpid;
 	pid_t		shm_cpid;
-	int		shm_nattch;
+	unsigned int	shm_nattch;
 	int32_t		shm_atime;
 	int32_t		shm_dtime;
 	int32_t		shm_ctime;
diff --git a/sys/kern/sysv_shm.c b/sys/kern/sysv_shm.c
index 4232a7f95234..24ece36e7f02 100644
--- a/sys/kern/sysv_shm.c
+++ b/sys/kern/sysv_shm.c
@@ -275,7 +275,7 @@ shm_delete_mapping(struct vmspace *vm, struct shmmap_state *shmmap_s)
 		return (EINVAL);
 	shmmap_s->shmid = -1;
 	shmseg->u.shm_dtime = time_second;
-	if ((--shmseg->u.shm_nattch <= 0) &&
+	if (--shmseg->u.shm_nattch == 0 &&
 	    (shmseg->u.shm_perm.mode & SHMSEG_REMOVED)) {
 		shm_deallocate_segment(shmseg);
 		shm_last_free = segnum;
@@ -289,7 +289,7 @@ shm_remove(struct shmid_kernel *shmseg, int segnum)
 
 	shmseg->u.shm_perm.key = IPC_PRIVATE;
 	shmseg->u.shm_perm.mode |= SHMSEG_REMOVED;
-	if (shmseg->u.shm_nattch <= 0) {
+	if (shmseg->u.shm_nattch == 0) {
 		shm_deallocate_segment(shmseg);
 		shm_last_free = segnum;
 	}
diff --git a/sys/sys/shm.h b/sys/sys/shm.h
index abf5a85b0d84..218be51a397a 100644
--- a/sys/sys/shm.h
+++ b/sys/sys/shm.h
@@ -92,12 +92,14 @@ struct shmid_ds_old {
 };
 #endif
 
+typedef unsigned int shmatt_t;
+
 struct shmid_ds {
 	struct ipc_perm shm_perm;	/* operation permission structure */
 	size_t          shm_segsz;	/* size of segment in bytes */
 	pid_t           shm_lpid;   /* process ID of last shared memory op */
 	pid_t           shm_cpid;	/* process ID of creator */
-	int		shm_nattch;	/* number of current attaches */
+	shmatt_t        shm_nattch;	/* number of current attaches */
 	time_t          shm_atime;	/* time of last shmat() */
 	time_t          shm_dtime;	/* time of last shmdt() */
 	time_t          shm_ctime;	/* time of last change by shmctl() */