diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1283,7 +1283,7 @@
 /*
  * Returns whether gid designates a supplementary group in cred.
  */
-static int
+static bool
 supplementary_group_member(gid_t gid, struct ucred *cred)
 {
 	int l, h, m;
@@ -1310,12 +1310,12 @@
  * Check if gid is a member of the (effective) group set (i.e., effective and
  * supplementary groups).
  */
-int
+bool
 groupmember(gid_t gid, struct ucred *cred)
 {
 
-	if (cred->cr_groups[0] == gid)
-		return (1);
+	if (gid == cred->cr_groups[0])
+		return (true);
 
 	return (supplementary_group_member(gid, cred));
 }
@@ -1324,11 +1324,11 @@
  * Check if gid is a member of the real group set (i.e., real and supplementary
  * groups).
  */
-int
+bool
 realgroupmember(gid_t gid, struct ucred *cred)
 {
 	if (gid == cred->cr_rgid)
-		return (1);
+		return (true);
 
 	return (supplementary_group_member(gid, cred));
 }
diff --git a/sys/sys/ucred.h b/sys/sys/ucred.h
--- a/sys/sys/ucred.h
+++ b/sys/sys/ucred.h
@@ -159,8 +159,8 @@
 void	cru2x(struct ucred *cr, struct xucred *xcr);
 void	cru2xt(struct thread *td, struct xucred *xcr);
 void	crsetgroups(struct ucred *cr, int n, gid_t *groups);
-int	groupmember(gid_t gid, struct ucred *cred);
-int	realgroupmember(gid_t gid, struct ucred *cred);
+bool	groupmember(gid_t gid, struct ucred *cred);
+bool	realgroupmember(gid_t gid, struct ucred *cred);
 #endif /* _KERNEL */
 
 #endif /* !_SYS_UCRED_H_ */