diff --git a/abstract_client.h b/abstract_client.h
--- a/abstract_client.h
+++ b/abstract_client.h
@@ -460,6 +460,7 @@
     virtual QRect iconGeometry() const;
     virtual bool userCanSetFullScreen() const = 0;
     virtual bool userCanSetNoBorder() const = 0;
+    virtual void checkNoBorder();
     virtual void setOnActivities(QStringList newActivitiesList);
     virtual void setOnAllActivities(bool set) = 0;
     const WindowRules* rules() const {
diff --git a/abstract_client.cpp b/abstract_client.cpp
--- a/abstract_client.cpp
+++ b/abstract_client.cpp
@@ -1797,4 +1797,9 @@
     Q_UNUSED(newActivitiesList)
 }
 
+void AbstractClient::checkNoBorder()
+{
+    setNoBorder(false);
+}
+
 }
diff --git a/client.h b/client.h
--- a/client.h
+++ b/client.h
@@ -162,7 +162,7 @@
     bool noBorder() const override;
     void setNoBorder(bool set) override;
     bool userCanSetNoBorder() const override;
-    void checkNoBorder();
+    void checkNoBorder() override;
 
     int sessionStackingOrder() const;
 
diff --git a/workspace.cpp b/workspace.cpp
--- a/workspace.cpp
+++ b/workspace.cpp
@@ -865,8 +865,8 @@
             !options->borderlessMaximizedWindows()) {
         // in case borderless maximized windows option changed and new option
         // is to have borders, we need to unset the borders for all maximized windows
-        for (ClientList::Iterator it = clients.begin();
-                it != clients.end();
+        for (auto it = m_allClients.begin();
+                it != m_allClients.end();
                 ++it) {
             if ((*it)->maximizeMode() == MaximizeFull)
                 (*it)->checkNoBorder();