diff --git a/src/core/display.c b/src/core/display.c
index e9197304c..e0dfc7c7e 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -2494,6 +2494,7 @@ meta_display_sanity_check_timestamps (MetaDisplay *display,
               meta_warning ("%s appears to be one of the offending windows "
                             "with a timestamp of %u.  Working around...",
                             window->desc, window->net_wm_user_time);
+              window->net_wm_user_time_set = FALSE;
               meta_window_set_user_time (window, timestamp);
             }