diff --git a/vnc.c b/vnc.c
index c54c6e0..58eac73 100644
--- a/vnc.c
+++ b/vnc.c
@@ -2305,6 +2305,10 @@ static void vnc_refresh(void *opaque)
         rects += vnc_update_client(vs, has_dirty);
         vs = vs->next;
     }
+    /* vd->timer could be NULL now if the last client disconnected,
+     * in this case don't update the timer */
+    if (vd->timer == NULL)
+        return;
 
     if (has_dirty && rects) {
         vd->timer_interval /= 2;