diff --git a/clientgroup.h b/clientgroup.h
index 49d346a077..718216eda3 100644
--- a/clientgroup.h
+++ b/clientgroup.h
@@ -210,7 +210,7 @@ inline QList< ClientGroupItem > ClientGroup::items() const
 
 inline Client* ClientGroup::visible()
 {
-    return clients_[visible_];
+    return clients_.at(visible_);
 }
 
 inline QSize ClientGroup::minSize() const