diff --git a/autotests/integration/stacking_order_test.cpp b/autotests/integration/stacking_order_test.cpp
index 10f2a3a7c2..4ed392bfab 100644
--- a/autotests/integration/stacking_order_test.cpp
+++ b/autotests/integration/stacking_order_test.cpp
@@ -360,7 +360,7 @@ void StackingOrderTest::testGroupTransientIsAboveWindowGroup()
     X11Client *leader = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(leader);
     QVERIFY(leader->isActive());
-    QCOMPARE(leader->windowId(), leaderWid);
+    QCOMPARE(leader->window(), leaderWid);
     QVERIFY(!leader->isTransient());
 
     QCOMPARE(workspace()->stackingOrder(), (QList<Toplevel *>{leader}));
@@ -375,7 +375,7 @@ void StackingOrderTest::testGroupTransientIsAboveWindowGroup()
     X11Client *member1 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member1);
     QVERIFY(member1->isActive());
-    QCOMPARE(member1->windowId(), member1Wid);
+    QCOMPARE(member1->window(), member1Wid);
     QCOMPARE(member1->group(), leader->group());
     QVERIFY(!member1->isTransient());
 
@@ -391,7 +391,7 @@ void StackingOrderTest::testGroupTransientIsAboveWindowGroup()
     X11Client *member2 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member2);
     QVERIFY(member2->isActive());
-    QCOMPARE(member2->windowId(), member2Wid);
+    QCOMPARE(member2->window(), member2Wid);
     QCOMPARE(member2->group(), leader->group());
     QVERIFY(!member2->isTransient());
 
@@ -429,7 +429,7 @@ void StackingOrderTest::testGroupTransientIsAboveWindowGroup()
     X11Client *transient = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(transient);
     QVERIFY(transient->isActive());
-    QCOMPARE(transient->windowId(), transientWid);
+    QCOMPARE(transient->window(), transientWid);
     QCOMPARE(transient->group(), leader->group());
     QVERIFY(transient->isTransient());
     QVERIFY(transient->groupTransient());
@@ -474,7 +474,7 @@ void StackingOrderTest::testRaiseGroupTransient()
     X11Client *leader = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(leader);
     QVERIFY(leader->isActive());
-    QCOMPARE(leader->windowId(), leaderWid);
+    QCOMPARE(leader->window(), leaderWid);
     QVERIFY(!leader->isTransient());
 
     QCOMPARE(workspace()->stackingOrder(), (QList<Toplevel *>{leader}));
@@ -489,7 +489,7 @@ void StackingOrderTest::testRaiseGroupTransient()
     X11Client *member1 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member1);
     QVERIFY(member1->isActive());
-    QCOMPARE(member1->windowId(), member1Wid);
+    QCOMPARE(member1->window(), member1Wid);
     QCOMPARE(member1->group(), leader->group());
     QVERIFY(!member1->isTransient());
 
@@ -505,7 +505,7 @@ void StackingOrderTest::testRaiseGroupTransient()
     X11Client *member2 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member2);
     QVERIFY(member2->isActive());
-    QCOMPARE(member2->windowId(), member2Wid);
+    QCOMPARE(member2->window(), member2Wid);
     QCOMPARE(member2->group(), leader->group());
     QVERIFY(!member2->isTransient());
 
@@ -543,7 +543,7 @@ void StackingOrderTest::testRaiseGroupTransient()
     X11Client *transient = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(transient);
     QVERIFY(transient->isActive());
-    QCOMPARE(transient->windowId(), transientWid);
+    QCOMPARE(transient->window(), transientWid);
     QCOMPARE(transient->group(), leader->group());
     QVERIFY(transient->isTransient());
     QVERIFY(transient->groupTransient());
@@ -608,7 +608,7 @@ void StackingOrderTest::testDeletedGroupTransient()
     X11Client *leader = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(leader);
     QVERIFY(leader->isActive());
-    QCOMPARE(leader->windowId(), leaderWid);
+    QCOMPARE(leader->window(), leaderWid);
     QVERIFY(!leader->isTransient());
 
     QCOMPARE(workspace()->stackingOrder(), (QList<Toplevel *>{leader}));
@@ -623,7 +623,7 @@ void StackingOrderTest::testDeletedGroupTransient()
     X11Client *member1 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member1);
     QVERIFY(member1->isActive());
-    QCOMPARE(member1->windowId(), member1Wid);
+    QCOMPARE(member1->window(), member1Wid);
     QCOMPARE(member1->group(), leader->group());
     QVERIFY(!member1->isTransient());
 
@@ -639,7 +639,7 @@ void StackingOrderTest::testDeletedGroupTransient()
     X11Client *member2 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member2);
     QVERIFY(member2->isActive());
-    QCOMPARE(member2->windowId(), member2Wid);
+    QCOMPARE(member2->window(), member2Wid);
     QCOMPARE(member2->group(), leader->group());
     QVERIFY(!member2->isTransient());
 
@@ -677,7 +677,7 @@ void StackingOrderTest::testDeletedGroupTransient()
     X11Client *transient = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(transient);
     QVERIFY(transient->isActive());
-    QCOMPARE(transient->windowId(), transientWid);
+    QCOMPARE(transient->window(), transientWid);
     QCOMPARE(transient->group(), leader->group());
     QVERIFY(transient->isTransient());
     QVERIFY(transient->groupTransient());
@@ -728,7 +728,7 @@ void StackingOrderTest::testDontKeepAboveNonModalDialogGroupTransients()
     X11Client *leader = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(leader);
     QVERIFY(leader->isActive());
-    QCOMPARE(leader->windowId(), leaderWid);
+    QCOMPARE(leader->window(), leaderWid);
     QVERIFY(!leader->isTransient());
 
     QCOMPARE(workspace()->stackingOrder(), (QList<Toplevel *>{leader}));
@@ -743,7 +743,7 @@ void StackingOrderTest::testDontKeepAboveNonModalDialogGroupTransients()
     X11Client *member1 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member1);
     QVERIFY(member1->isActive());
-    QCOMPARE(member1->windowId(), member1Wid);
+    QCOMPARE(member1->window(), member1Wid);
     QCOMPARE(member1->group(), leader->group());
     QVERIFY(!member1->isTransient());
 
@@ -759,7 +759,7 @@ void StackingOrderTest::testDontKeepAboveNonModalDialogGroupTransients()
     X11Client *member2 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(member2);
     QVERIFY(member2->isActive());
-    QCOMPARE(member2->windowId(), member2Wid);
+    QCOMPARE(member2->window(), member2Wid);
     QCOMPARE(member2->group(), leader->group());
     QVERIFY(!member2->isTransient());
 
@@ -776,7 +776,7 @@ void StackingOrderTest::testDontKeepAboveNonModalDialogGroupTransients()
     X11Client *transient = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(transient);
     QVERIFY(transient->isActive());
-    QCOMPARE(transient->windowId(), transientWid);
+    QCOMPARE(transient->window(), transientWid);
     QCOMPARE(transient->group(), leader->group());
     QVERIFY(transient->isTransient());
     QVERIFY(transient->groupTransient());
diff --git a/autotests/integration/x11_client_test.cpp b/autotests/integration/x11_client_test.cpp
index ee79221008..34faf2f01f 100644
--- a/autotests/integration/x11_client_test.cpp
+++ b/autotests/integration/x11_client_test.cpp
@@ -726,7 +726,7 @@ void X11ClientTest::testX11WindowId()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client);
-    QCOMPARE(client->windowId(), w);
+    QCOMPARE(client->window(), w);
     QVERIFY(client->isActive());
     QCOMPARE(client->window(), w);
     QCOMPARE(client->internalId().isNull(), false);
@@ -801,7 +801,7 @@ void X11ClientTest::testCaptionChanges()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client);
-    QCOMPARE(client->windowId(), w);
+    QCOMPARE(client->window(), w);
     QCOMPARE(client->caption(), QStringLiteral("foo"));
 
     QSignalSpy captionChangedSpy(client, &X11Client::captionChanged);
@@ -873,7 +873,7 @@ void X11ClientTest::testCaptionMultipleWindows()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client);
-    QCOMPARE(client->windowId(), w);
+    QCOMPARE(client->window(), w);
     QCOMPARE(client->caption(), QStringLiteral("foo"));
 
     // create second window with same caption
@@ -895,7 +895,7 @@ void X11ClientTest::testCaptionMultipleWindows()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client2 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client2);
-    QCOMPARE(client2->windowId(), w2);
+    QCOMPARE(client2->window(), w2);
     QCOMPARE(client2->caption(), QStringLiteral("foo <2>\u200E"));
     NETWinInfo info3(kwinApp()->x11Connection(), w2, kwinApp()->x11RootWindow(), NET::WMVisibleName | NET::WMVisibleIconName, NET::Properties2());
     QCOMPARE(QByteArray(info3.visibleName()), QByteArrayLiteral("foo <2>\u200E"));
@@ -948,7 +948,7 @@ void X11ClientTest::testFullscreenWindowGroups()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client);
-    QCOMPARE(client->windowId(), w);
+    QCOMPARE(client->window(), w);
     QCOMPARE(client->isActive(), true);
 
     QCOMPARE(client->isFullScreen(), false);
@@ -979,7 +979,7 @@ void X11ClientTest::testFullscreenWindowGroups()
     X11Client *client2 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client2);
     QVERIFY(client != client2);
-    QCOMPARE(client2->windowId(), w2);
+    QCOMPARE(client2->window(), w2);
     QCOMPARE(client2->isActive(), true);
     QCOMPARE(client2->group(), client->group());
     // first client should be moved back to normal layer
@@ -1024,7 +1024,7 @@ void X11ClientTest::testActivateFocusedWindow()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client1 = windowCreatedSpy.first().first().value<X11Client *>();
     QVERIFY(client1);
-    QCOMPARE(client1->windowId(), window1);
+    QCOMPARE(client1->window(), window1);
     QCOMPARE(client1->isActive(), true);
 
     // Create the second test window.
@@ -1041,7 +1041,7 @@ void X11ClientTest::testActivateFocusedWindow()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client2 = windowCreatedSpy.last().first().value<X11Client *>();
     QVERIFY(client2);
-    QCOMPARE(client2->windowId(), window2);
+    QCOMPARE(client2->window(), window2);
     QCOMPARE(client2->isActive(), true);
 
     // When the second test window is destroyed, the window manager will attempt to activate the
diff --git a/autotests/integration/xdgshellclient_test.cpp b/autotests/integration/xdgshellclient_test.cpp
index 499c89be07..e94865b416 100644
--- a/autotests/integration/xdgshellclient_test.cpp
+++ b/autotests/integration/xdgshellclient_test.cpp
@@ -80,7 +80,6 @@ private Q_SLOTS:
     void testCaptionMultipleWindows();
     void testUnresponsiveWindow_data();
     void testUnresponsiveWindow();
-    void testX11WindowId();
     void testAppMenu();
     void testNoDecorationModeRequested();
     void testSendClientWithTransientToDesktop();
@@ -864,16 +863,6 @@ void TestXdgShellClient::testUnresponsiveWindow()
     QVERIFY(elapsed2 > 1800); //second ping comes in a second later
 }
 
-void TestXdgShellClient::testX11WindowId()
-{
-    QScopedPointer<Surface> surface(Test::createSurface());
-    QScopedPointer<XdgShellSurface> shellSurface(Test::createXdgShellStableSurface(surface.data()));
-    auto c = Test::renderAndWaitForShown(surface.data(), QSize(100, 50), Qt::blue);
-    QVERIFY(c);
-    QVERIFY(c->windowId() != 0);
-    QCOMPARE(c->window(), 0u);
-}
-
 void TestXdgShellClient::testAppMenu()
 {
     //register a faux appmenu client
diff --git a/autotests/integration/xwaylandserver_restart_test.cpp b/autotests/integration/xwaylandserver_restart_test.cpp
index d268320307..d197ee5c3f 100644
--- a/autotests/integration/xwaylandserver_restart_test.cpp
+++ b/autotests/integration/xwaylandserver_restart_test.cpp
@@ -102,7 +102,7 @@ void XwaylandServerRestartTest::testRestart()
     QVERIFY(windowCreatedSpy.wait());
     X11Client *client = windowCreatedSpy.last().first().value<X11Client *>();
     QVERIFY(client);
-    QCOMPARE(client->windowId(), window);
+    QCOMPARE(client->window(), window);
     QVERIFY(client->isDecorated());
 
     // Render a frame to ensure that the compositor doesn't crash.
diff --git a/decorations/decoratedclient.cpp b/decorations/decoratedclient.cpp
index d33a8884a0..d9072ca5e6 100644
--- a/decorations/decoratedclient.cpp
+++ b/decorations/decoratedclient.cpp
@@ -163,7 +163,7 @@ DELEGATE2(QIcon, icon)
 DELEGATE(bool, isKeepAbove, keepAbove)
 DELEGATE(bool, isKeepBelow, keepBelow)
 DELEGATE(bool, isShaded, isShade)
-DELEGATE(WId, windowId, windowId)
+DELEGATE(WId, windowId, window)
 DELEGATE(WId, decorationId, frameId)
 
 #undef DELEGATE
diff --git a/effects.cpp b/effects.cpp
index 5cd17d6f4c..a06437ae1d 100644
--- a/effects.cpp
+++ b/effects.cpp
@@ -1053,11 +1053,6 @@ EffectWindow* EffectsHandlerImpl::findWindow(WId id) const
         return w->effectWindow();
     if (Unmanaged* w = Workspace::self()->findUnmanaged(id))
         return w->effectWindow();
-    if (waylandServer()) {
-        if (AbstractClient *w = waylandServer()->findClient(id)) {
-            return w->effectWindow();
-        }
-    }
     return nullptr;
 }
 
diff --git a/events.cpp b/events.cpp
index b2117489aa..0851bfd92d 100644
--- a/events.cpp
+++ b/events.cpp
@@ -1173,7 +1173,7 @@ void X11Client::focusInEvent(xcb_focus_in_event_t *e)
         if (workspace()->restoreFocus()) {
             demandAttention();
         } else {
-            qCWarning(KWIN_CORE, "Failed to restore focus. Activating 0x%x", windowId());
+            qCWarning(KWIN_CORE, "Failed to restore focus. Activating 0x%x", window());
             setActive(true);
         }
     }
diff --git a/internal_client.cpp b/internal_client.cpp
index 3391de4817..70fcfaff7b 100644
--- a/internal_client.cpp
+++ b/internal_client.cpp
@@ -27,7 +27,6 @@ namespace KWin
 
 InternalClient::InternalClient(QWindow *window)
     : m_internalWindow(window)
-    , m_windowId(window->winId())
     , m_internalWindowFlags(window->flags())
 {
     connect(m_internalWindow, &QWindow::xChanged, this, &InternalClient::updateInternalWindowGeometry);
@@ -252,11 +251,6 @@ bool InternalClient::isOutline() const
     return false;
 }
 
-quint32 InternalClient::windowId() const
-{
-    return m_windowId;
-}
-
 bool InternalClient::isShown(bool shaded_is_shown) const
 {
     Q_UNUSED(shaded_is_shown)
diff --git a/internal_client.h b/internal_client.h
index 7433c70b08..034afd0dfd 100644
--- a/internal_client.h
+++ b/internal_client.h
@@ -52,7 +52,6 @@ public:
     bool isInternal() const override;
     bool isLockScreen() const override;
     bool isOutline() const override;
-    quint32 windowId() const override;
     bool isShown(bool shaded_is_shown) const override;
     bool isHiddenInternal() const override;
     void hideClient(bool hide) override;
@@ -89,7 +88,6 @@ private:
     QString m_captionSuffix;
     double m_opacity = 1.0;
     NET::WindowType m_windowType = NET::Normal;
-    quint32 m_windowId = 0;
     Qt::WindowFlags m_internalWindowFlags = Qt::WindowFlags();
     bool m_userNoBorder = false;
 
diff --git a/toplevel.cpp b/toplevel.cpp
index 5b3884533c..c0a90627cc 100644
--- a/toplevel.cpp
+++ b/toplevel.cpp
@@ -66,7 +66,9 @@ QDebug operator<<(QDebug debug, const Toplevel *toplevel)
     debug.nospace();
     if (toplevel) {
         debug << toplevel->metaObject()->className() << '(' << static_cast<const void *>(toplevel);
-        debug << ", windowId=0x" << Qt::hex << toplevel->windowId() << Qt::dec;
+        if (toplevel->window()) {
+            debug << ", windowId=0x" << Qt::hex << toplevel->window() << Qt::dec;
+        }
         if (const KWaylandServer::SurfaceInterface *surface = toplevel->surface()) {
             debug << ", surface=" << surface;
         }
@@ -809,11 +811,6 @@ QPointF Toplevel::mapToLocal(const QPointF &point) const
     return point - bufferGeometry().topLeft();
 }
 
-quint32 Toplevel::windowId() const
-{
-    return window();
-}
-
 QRect Toplevel::inputGeometry() const
 {
     return frameGeometry();
diff --git a/toplevel.h b/toplevel.h
index bfd8e0ee32..5ec016a046 100644
--- a/toplevel.h
+++ b/toplevel.h
@@ -112,7 +112,7 @@ class KWIN_EXPORT Toplevel : public QObject
     Q_PROPERTY(QRect visibleRect READ visibleRect)
     Q_PROPERTY(qreal opacity READ opacity WRITE setOpacity NOTIFY opacityChanged)
     Q_PROPERTY(int screen READ screen NOTIFY screenChanged)
-    Q_PROPERTY(qulonglong windowId READ windowId CONSTANT)
+    Q_PROPERTY(qulonglong windowId READ window CONSTANT)
     Q_PROPERTY(int desktop READ desktop)
 
     /**
@@ -295,10 +295,6 @@ public:
     explicit Toplevel();
     virtual xcb_window_t frameId() const;
     xcb_window_t window() const;
-    /**
-     * @return a unique identifier for the Toplevel. On X11 same as @ref window
-     */
-    virtual quint32 windowId() const;
     /**
      * Returns the geometry of the pixmap or buffer attached to this Toplevel.
      *
diff --git a/useractions.cpp b/useractions.cpp
index 885237adc5..f4707f3a97 100644
--- a/useractions.cpp
+++ b/useractions.cpp
@@ -188,7 +188,7 @@ void UserActionsMenu::helperDialog(const QString& message, AbstractClient* clien
         args << QStringLiteral("--dontagain") << QLatin1String("kwin_dialogsrc:") + type;
     }
     if (client)
-        args << QStringLiteral("--embed") << QString::number(client->windowId());
+        args << QStringLiteral("--embed") << QString::number(client->window());
     QtConcurrent::run([args]() {
         KProcess::startDetached(QStringLiteral("kdialog"), args);
     });
diff --git a/wayland_server.cpp b/wayland_server.cpp
index 42f0356095..afb97ff280 100644
--- a/wayland_server.cpp
+++ b/wayland_server.cpp
@@ -748,19 +748,6 @@ void WaylandServer::dispatch()
     m_display->dispatchEvents(0);
 }
 
-static AbstractClient *findClientInList(const QList<AbstractClient *> &clients, quint32 id)
-{
-    auto it = std::find_if(clients.begin(), clients.end(),
-        [id] (AbstractClient *c) {
-            return c->windowId() == id;
-        }
-    );
-    if (it == clients.end()) {
-        return nullptr;
-    }
-    return *it;
-}
-
 static AbstractClient *findClientInList(const QList<AbstractClient *> &clients, KWaylandServer::SurfaceInterface *surface)
 {
     auto it = std::find_if(clients.begin(), clients.end(),
@@ -774,17 +761,6 @@ static AbstractClient *findClientInList(const QList<AbstractClient *> &clients,
     return *it;
 }
 
-AbstractClient *WaylandServer::findClient(quint32 id) const
-{
-    if (id == 0) {
-        return nullptr;
-    }
-    if (AbstractClient *c = findClientInList(m_clients, id)) {
-        return c;
-    }
-    return nullptr;
-}
-
 AbstractClient *WaylandServer::findClient(SurfaceInterface *surface) const
 {
     if (!surface) {
@@ -806,48 +782,6 @@ XdgSurfaceClient *WaylandServer::findXdgSurfaceClient(SurfaceInterface *surface)
     return qobject_cast<XdgSurfaceClient *>(findClient(surface));
 }
 
-quint32 WaylandServer::createWindowId(SurfaceInterface *surface)
-{
-    auto it = m_clientIds.constFind(surface->client());
-    quint16 clientId = 0;
-    if (it != m_clientIds.constEnd()) {
-        clientId = it.value();
-    } else {
-        clientId = createClientId(surface->client());
-    }
-    Q_ASSERT(clientId != 0);
-    quint32 id = clientId;
-    // TODO: this does not prevent that two surfaces of same client get same id
-    id = (id << 16) | (surface->id() & 0xFFFF);
-    if (findClient(id)) {
-        qCWarning(KWIN_CORE) << "Invalid client windowId generated:" << id;
-        return 0;
-    }
-    return id;
-}
-
-quint16 WaylandServer::createClientId(ClientConnection *c)
-{
-    const QSet<unsigned short> ids(m_clientIds.constBegin(), m_clientIds.constEnd());
-    quint16 id = 1;
-    if (!ids.isEmpty()) {
-        for (quint16 i = ids.count() + 1; i >= 1 ; i--) {
-            if (!ids.contains(i)) {
-                id = i;
-                break;
-            }
-        }
-    }
-    Q_ASSERT(!ids.contains(id));
-    m_clientIds.insert(c, id);
-    connect(c, &ClientConnection::disconnected, this,
-        [this] (ClientConnection *c) {
-            m_clientIds.remove(c);
-        }
-    );
-    return id;
-}
-
 bool WaylandServer::isScreenLocked() const
 {
     if (!hasScreenLockerIntegration()) {
diff --git a/wayland_server.h b/wayland_server.h
index bb677929ac..26ddbc67d5 100644
--- a/wayland_server.h
+++ b/wayland_server.h
@@ -142,7 +142,6 @@ public:
         return m_clients;
     }
     void removeClient(AbstractClient *c);
-    AbstractClient *findClient(quint32 id) const;
     AbstractClient *findClient(KWaylandServer::SurfaceInterface *surface) const;
     XdgToplevelClient *findXdgToplevelClient(KWaylandServer::SurfaceInterface *surface) const;
     XdgSurfaceClient *findXdgSurfaceClient(KWaylandServer::SurfaceInterface *surface) const;
@@ -207,7 +206,6 @@ public:
         return m_internalConnection.registry;
     }
     void dispatch();
-    quint32 createWindowId(KWaylandServer::SurfaceInterface *surface);
 
     /**
      * Struct containing information for a created Wayland connection through a
@@ -253,7 +251,6 @@ Q_SIGNALS:
 private:
     int createScreenLockerConnection();
     void shellClientShown(Toplevel *t);
-    quint16 createClientId(KWaylandServer::ClientConnection *c);
     void destroyInternalConnection();
     void initScreenLocker();
     void registerXdgGenericClient(AbstractClient *client);
@@ -296,7 +293,6 @@ private:
     KWaylandServer::XdgForeignV2Interface *m_XdgForeign = nullptr;
     KWaylandServer::KeyStateInterface *m_keyState = nullptr;
     QList<AbstractClient *> m_clients;
-    QHash<KWaylandServer::ClientConnection*, quint16> m_clientIds;
     InitializationFlags m_initFlags;
     QVector<KWaylandServer::PlasmaShellSurfaceInterface*> m_plasmaShellSurfaces;
     KWIN_SINGLETON(WaylandServer)
diff --git a/waylandclient.cpp b/waylandclient.cpp
index 681165f3fd..55778be858 100644
--- a/waylandclient.cpp
+++ b/waylandclient.cpp
@@ -44,8 +44,6 @@ WaylandClient::WaylandClient(SurfaceInterface *surface)
     setSurface(surface);
     setupCompositing();
 
-    m_windowId = waylandServer()->createWindowId(surface);
-
     connect(surface, &SurfaceInterface::shadowChanged,
             this, &WaylandClient::updateShadow);
     connect(this, &WaylandClient::frameGeometryChanged,
@@ -94,11 +92,6 @@ QRect WaylandClient::transparentRect() const
     return QRect();
 }
 
-quint32 WaylandClient::windowId() const
-{
-    return m_windowId;
-}
-
 pid_t WaylandClient::pid() const
 {
     return surface()->client()->processId();
diff --git a/waylandclient.h b/waylandclient.h
index eb566af41a..9701d06439 100644
--- a/waylandclient.h
+++ b/waylandclient.h
@@ -31,7 +31,6 @@ public:
     void blockActivityUpdates(bool b = true) override;
     QPoint clientContentPos() const override;
     QRect transparentRect() const override;
-    quint32 windowId() const override;
     pid_t pid() const override;
     bool isLockScreen() const override;
     bool isLocalhost() const override;
@@ -88,7 +87,6 @@ private:
     QRect m_requestedClientGeometry;
     SyncMode m_positionSyncMode = SyncMode::Sync;
     SyncMode m_sizeSyncMode = SyncMode::Sync;
-    quint32 m_windowId;
     bool m_isHidden = false;
 };
 
diff --git a/x11client.cpp b/x11client.cpp
index fdb40bc39b..55618ff833 100644
--- a/x11client.cpp
+++ b/x11client.cpp
@@ -2015,10 +2015,10 @@ bool X11Client::takeFocus()
     if (rules()->checkAcceptFocus(info->input())) {
         xcb_void_cookie_t cookie = xcb_set_input_focus_checked(connection(),
                                                                XCB_INPUT_FOCUS_POINTER_ROOT,
-                                                               windowId(), XCB_TIME_CURRENT_TIME);
+                                                               window(), XCB_TIME_CURRENT_TIME);
         ScopedCPointer<xcb_generic_error_t> error(xcb_request_check(connection(), cookie));
         if (error) {
-            qCWarning(KWIN_CORE, "Failed to focus 0x%x (error %d)", windowId(), error->error_code);
+            qCWarning(KWIN_CORE, "Failed to focus 0x%x (error %d)", window(), error->error_code);
             return false;
         }
     } else {