--- a/twoprocess.c
+++ b/twoprocess.c
@@ -426,7 +426,7 @@ common_do_login(struct vsf_session* p_sess, const struct mystr* p_user_str,
      */
     vsf_set_die_if_parent_dies();
     priv_sock_set_child_context(p_sess);
-    if (tunable_guest_enable && !anon)
+    if (tunable_guest_enable && !anon && !str_getpwnam(p_user_str))
     {
       p_sess->is_guest = 1;
       /* Remap to the guest user */