diff --git a/src/win.c b/src/win.c
index c69365f..c6b9bfa 100644
--- a/src/win.c
+++ b/src/win.c
@@ -623,7 +623,7 @@ void win_on_win_size_change(session_t *ps, win *w) {
       backend_list[ps->o.backend]->release_win(ps->backend_data, ps, w, w->win_data);
       w->win_data = backend_list[ps->o.backend]->prepare_win(ps->backend_data, ps, w);
     } else {
-      assert(false);
+      assert(w->state == WSTATE_UNMAPPED);
     }
   } else {
     free_paint(ps, &w->shadow_paint);