diff --git a/share/man/man9/groupmember.9 b/share/man/man9/groupmember.9
--- a/share/man/man9/groupmember.9
+++ b/share/man/man9/groupmember.9
@@ -25,7 +25,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 .\" DAMAGE.
 .\"
-.Dd August 18, 2023
+.Dd October 31, 2024
 .Dt GROUPMEMBER 9
 .Os
 .Sh NAME
@@ -35,9 +35,9 @@
 .In sys/param.h
 .In sys/ucred.h
 .Ft bool
-.Fn groupmember "gid_t gid" "struct ucred *cred"
+.Fn groupmember "gid_t gid" "const struct ucred *cred"
 .Ft bool
-.Fn realgroupmember "gid_t gid" "struct ucred *cred"
+.Fn realgroupmember "gid_t gid" "const struct ucred *cred"
 .Sh DESCRIPTION
 The
 .Fn groupmember
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
@@ -1307,7 +1307,7 @@
  * supplementary groups).
  */
 bool
-groupmember(gid_t gid, struct ucred *cred)
+groupmember(gid_t gid, const struct ucred *cred)
 {
 
 	/*
@@ -1328,7 +1328,7 @@
  * groups).
  */
 bool
-realgroupmember(gid_t gid, struct ucred *cred)
+realgroupmember(gid_t gid, const struct ucred *cred)
 {
 	if (gid == cred->cr_rgid)
 		return (true);
diff --git a/sys/sys/ucred.h b/sys/sys/ucred.h
--- a/sys/sys/ucred.h
+++ b/sys/sys/ucred.h
@@ -155,8 +155,8 @@
 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);
-bool	groupmember(gid_t gid, struct ucred *cred);
-bool	realgroupmember(gid_t gid, struct ucred *cred);
+bool	groupmember(gid_t gid, const struct ucred *cred);
+bool	realgroupmember(gid_t gid, const struct ucred *cred);
 #endif /* _KERNEL */
 
 #endif /* !_SYS_UCRED_H_ */