Index: abstract_client.h
===================================================================
--- abstract_client.h
+++ abstract_client.h
@@ -408,7 +408,7 @@
      *  or recursively the transient_for window
      * @todo: remove boolean trap
      **/
-    virtual bool hasTransient(const AbstractClient* c, bool indirect) const;
+    bool hasTransient(const AbstractClient* c, bool indirect) const;
     const QList<AbstractClient*>& transients() const; // Is not indirect
     virtual void removeTransient(AbstractClient* cl);
     virtual QList<AbstractClient*> mainClients() const; // Call once before loop , is not indirect
@@ -1131,6 +1131,7 @@
 
 private:
     void handlePaletteChange();
+    bool hasTransientInternal(const AbstractClient* c, bool indirect, QVector<const AbstractClient*> &set) const;
     QSharedPointer<TabBox::TabBoxClientImpl> m_tabBoxClient;
     bool m_firstInTabBox = false;
     bool m_skipTaskbar = false;
Index: abstract_client.cpp
===================================================================
--- abstract_client.cpp
+++ abstract_client.cpp
@@ -1287,10 +1287,46 @@
     return QRect();
 }
 
-bool AbstractClient::hasTransient(const AbstractClient *c, bool indirect) const
+// returns true if cl is the transient_for window for this client,
+// or recursively the transient_for window
+bool AbstractClient::hasTransient(const AbstractClient* cl, bool indirect) const
 {
-    Q_UNUSED(indirect);
-    return c->transientFor() == this;
+    // checkGroupTransients() uses this to break loops, so hasTransient() must detect them
+    QVector<const AbstractClient*> set;
+    return hasTransientInternal(cl, indirect, set);
+}
+
+bool AbstractClient::hasTransientInternal(const AbstractClient* cl, bool indirect, QVector<const AbstractClient*>& set) const
+{
+    if (const auto *t = cl->transientFor()) {
+        if (t == this)
+            return true;
+        if (!indirect)
+            return false;
+        if (set.contains(cl))
+            return false;
+        set.append(cl);
+        return hasTransientInternal(t, indirect, set);
+    }
+    if (!cl->isTransient())
+        return false;
+    if (group() != cl->group())
+        return false;
+    // cl is group transient, search from top
+    if (transients().contains(const_cast< AbstractClient* >(cl)))
+        return true;
+    if (!indirect)
+        return false;
+    if (set.contains(this))
+        return false;
+    set.append(this);
+    for (auto it = transients().constBegin();
+            it != transients().constEnd();
+            ++it) {
+        if ((*it)->hasTransientInternal(cl, indirect, set))
+            return true;
+    }
+    return false;
 }
 
 QList< AbstractClient* > AbstractClient::mainClients() const
Index: client.h
===================================================================
--- client.h
+++ client.h
@@ -96,7 +96,6 @@
     bool groupTransient() const override;
     bool wasOriginallyGroupTransient() const;
     QList<AbstractClient*> mainClients() const override; // Call once before loop , is not indirect
-    bool hasTransient(const AbstractClient* c, bool indirect) const override;
     void checkTransient(xcb_window_t w);
     AbstractClient* findModal(bool allow_itself = false) override;
     const Group* group() const override;
@@ -415,7 +414,6 @@
     void fetchIconicName();
     QString readName() const;
     void setCaption(const QString& s, bool force = false);
-    bool hasTransientInternal(const Client* c, bool indirect, ConstClientList& set) const;
     void setShortcutInternal() override;
 
     void configureRequest(int value_mask, int rx, int ry, int rw, int rh, int gravity, bool from_tool);
Index: group.cpp
===================================================================
--- group.cpp
+++ group.cpp
@@ -687,55 +687,6 @@
     setTransient(w);
 }
 
-// returns true if cl is the transient_for window for this client,
-// or recursively the transient_for window
-bool Client::hasTransient(const AbstractClient* cl, bool indirect) const
-{
-    if (const Client *c = dynamic_cast<const Client*>(cl)) {
-        // checkGroupTransients() uses this to break loops, so hasTransient() must detect them
-        ConstClientList set;
-        return hasTransientInternal(c, indirect, set);
-    }
-    return false;
-}
-
-bool Client::hasTransientInternal(const Client* cl, bool indirect, ConstClientList& set) const
-{
-    if (const Client *t = dynamic_cast<const Client*>(cl->transientFor())) {
-        if (t == this)
-            return true;
-        if (!indirect)
-            return false;
-        if (set.contains(cl))
-            return false;
-        set.append(cl);
-        return hasTransientInternal(t, indirect, set);
-    }
-    if (!cl->isTransient())
-        return false;
-    if (group() != cl->group())
-        return false;
-    // cl is group transient, search from top
-    if (transients().contains(const_cast< Client* >(cl)))
-        return true;
-    if (!indirect)
-        return false;
-    if (set.contains(this))
-        return false;
-    set.append(this);
-    for (auto it = transients().constBegin();
-            it != transients().constEnd();
-            ++it) {
-        const Client *c = qobject_cast<const Client *>(*it);
-        if (!c) {
-            continue;
-        }
-        if (c->hasTransientInternal(cl, indirect, set))
-            return true;
-    }
-    return false;
-}
-
 QList<AbstractClient*> Client::mainClients() const
 {
     if (!isTransient())