diff --git a/activation.cpp b/activation.cpp
--- a/activation.cpp
+++ b/activation.cpp
@@ -271,7 +271,7 @@
     updateStackingOrder(); // e.g. fullscreens have different layer when active/not-active
 
     if (rootInfo()) {
-        rootInfo()->setActiveWindow(active_client ? active_client->window() : 0);
+        rootInfo()->setActiveClient(active_client);
     }
 
     emit clientActivated(active_client);
diff --git a/netinfo.h b/netinfo.h
--- a/netinfo.h
+++ b/netinfo.h
@@ -30,6 +30,7 @@
 namespace KWin
 {
 
+class AbstractClient;
 class Client;
 
 /**
@@ -44,6 +45,8 @@
     static RootInfo *create();
     static void destroy();
 
+    void setActiveClient(AbstractClient *client);
+
 protected:
     virtual void changeNumberOfDesktops(int n) override;
     virtual void changeCurrentDesktop(int d) override;
@@ -60,6 +63,8 @@
              NET::States states, NET::Properties2 properties2, NET::Actions actions, int scr = -1);
     static RootInfo *s_self;
     friend RootInfo *rootInfo();
+
+    xcb_window_t m_activeWindow;
 };
 
 inline RootInfo *rootInfo()
diff --git a/netinfo.cpp b/netinfo.cpp
--- a/netinfo.cpp
+++ b/netinfo.cpp
@@ -138,6 +138,7 @@
 RootInfo::RootInfo(xcb_window_t w, const char *name, NET::Properties properties, NET::WindowTypes types,
                    NET::States states, NET::Properties2 properties2, NET::Actions actions, int scr)
     : NETRootInfo(connection(), w, name, properties, types, states, properties2, actions, scr)
+    , m_activeWindow(activeWindow())
 {
 }
 
@@ -224,6 +225,16 @@
     Workspace::self()->setShowingDesktop(showing);
 }
 
+void RootInfo::setActiveClient(AbstractClient *client)
+{
+    const xcb_window_t w = client ? client->window() : xcb_window_t{XCB_WINDOW_NONE};
+    if (m_activeWindow == w) {
+        return;
+    }
+    m_activeWindow = w;
+    setActiveWindow(m_activeWindow);
+}
+
 // ****************************************
 // WinInfo
 // ****************************************