diff --git a/usr.sbin/pw/pw_group.c b/usr.sbin/pw/pw_group.c
index 4ed6ea972986..b20ce88fb301 100644
--- a/usr.sbin/pw/pw_group.c
+++ b/usr.sbin/pw/pw_group.c
@@ -67,6 +67,11 @@ pw_group(struct userconf * cnf, int mode, struct cargs * args)
 		NULL
 	};
 
+	if (a_gid != NULL) {
+		if (strspn(a_gid->val, "0123456789") != strlen(a_gid->val))
+			errx(EX_USAGE, "-g expects a number");
+	}
+
 	if (mode == M_LOCK || mode == M_UNLOCK)
 		errx(EX_USAGE, "'lock' command is not available for groups");
 
diff --git a/usr.sbin/pw/tests/pw_delete.sh b/usr.sbin/pw/tests/pw_delete.sh
index 06366294bd4b..6ebbf24abb34 100755
--- a/usr.sbin/pw/tests/pw_delete.sh
+++ b/usr.sbin/pw/tests/pw_delete.sh
@@ -18,7 +18,19 @@ rmuser_seperate_group_body() {
 	pw -V ${HOME} userdel test || atf_fail "delete the user"
 }
 
+atf_test_case group_do_not_delete_wheel_if_group_unkown
+group_do_not_delete_wheel_if_group_unkown_head() {
+	atf_set "descr" "Make sure we do not consider as gid 0 an unknown group"
+}
+
+group_do_not_delete_wheel_if_group_unkown_body() {
+	populate_etc_skel
+	atf_check -s exit:0 -o inline:"wheel:*:0:root\n" -x pw -V ${HOME} groupshow wheel
+	atf_check -e inline:"pw: -g expects a number\n" -s exit:64 -x pw -V ${HOME} groupdel -g I_do_not_exist
+	atf_check -s exit:0 -o "wheel:*:0:root\n" -x pw -V ${HOME} groupshow wheel
+}
 
 atf_init_test_cases() {
 	atf_add_test_case rmuser_seperate_group
+	atf_add_test_case group_do_not_delete_wheel_if_group_unkown
 }