diff --git a/lib/libkvm/kvm_proc.c b/lib/libkvm/kvm_proc.c
--- a/lib/libkvm/kvm_proc.c
+++ b/lib/libkvm/kvm_proc.c
@@ -150,13 +150,14 @@
 			kp->ki_cr_flags = 0;
 			if (ucred.cr_flags & CRED_FLAG_CAPMODE)
 				kp->ki_cr_flags |= KI_CRF_CAPABILITY_MODE;
-			if (ucred.cr_ngroups > KI_NGROUPS) {
+			if (1 + ucred.cr_ngroups > KI_NGROUPS) {
 				kp->ki_ngroups = KI_NGROUPS;
 				kp->ki_cr_flags |= KI_CRF_GRP_OVERFLOW;
 			} else
-				kp->ki_ngroups = ucred.cr_ngroups;
-			kvm_read(kd, (u_long)ucred.cr_groups, kp->ki_groups,
-			    kp->ki_ngroups * sizeof(gid_t));
+				kp->ki_ngroups = 1 + ucred.cr_ngroups;
+			kp->ki_groups[0] = ucred.cr_gid;
+			kvm_read(kd, (u_long)ucred.cr_groups, kp->ki_groups + 1,
+			    (kp->ki_ngroups - 1) * sizeof(gid_t));
 			if (ucred.cr_prison != NULL) {
 				if (KREAD(kd, (u_long)ucred.cr_prison, &pr)) {
 					_kvm_err(kd, kd->program,