diff --git a/vnc.c b/vnc.c
index 83d001161e7f5a5e5ab7aa60a5b2829fb7a84ee5..88cca3b730711aa83e8d0f833e292b15d107ac5f 100644
--- a/vnc.c
+++ b/vnc.c
@@ -1806,7 +1806,10 @@ static int protocol_client_auth(VncState *vs, char *data, size_t len)
        switch (vs->auth) {
        case VNC_AUTH_NONE:
            VNC_DEBUG("Accept auth none\n");
-           vnc_write_u32(vs, 0); /* Accept auth completion */
+           if (vs->minor >= 8) {
+               vnc_write_u32(vs, 0); /* Accept auth completion */
+               vnc_flush(vs);
+           }
            vnc_read_when(vs, protocol_client_init, 1);
            break;