diff --git a/src/maomao.c b/src/maomao.c
index 1c7f563..c5c7e07 100644
--- a/src/maomao.c
+++ b/src/maomao.c
@@ -1077,7 +1077,7 @@ bool check_hit_no_border(Client *c) {
     }
   }
 
-  if (no_border_when_single && c->mon->visible_clients == 1) {
+  if (no_border_when_single && c && c->mon && c->mon->visible_clients == 1) {
     hit_no_border = true;
   }
   return hit_no_border;