diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -1112,13 +1112,14 @@
 		if (cred->cr_flags & CRED_FLAG_CAPMODE)
 			kp->ki_cr_flags |= KI_CRF_CAPABILITY_MODE;
 		/* XXX bde doesn't like KI_NGROUPS */
-		if (cred->cr_ngroups > KI_NGROUPS) {
+		if (1 + cred->cr_ngroups > KI_NGROUPS) {
 			kp->ki_ngroups = KI_NGROUPS;
 			kp->ki_cr_flags |= KI_CRF_GRP_OVERFLOW;
 		} else
-			kp->ki_ngroups = cred->cr_ngroups;
-		bcopy(cred->cr_groups, kp->ki_groups,
-		    kp->ki_ngroups * sizeof(gid_t));
+			kp->ki_ngroups = 1 + cred->cr_ngroups;
+		kp->ki_groups[0] = cred->cr_gid;
+		bcopy(cred->cr_groups, kp->ki_groups + 1,
+		    (kp->ki_ngroups - 1) * sizeof(gid_t));
 		kp->ki_rgid = cred->cr_rgid;
 		kp->ki_svgid = cred->cr_svgid;
 		/* If jailed(cred), emulate the old P_JAILED flag. */