diff --git a/abstract_client.h b/abstract_client.h
--- a/abstract_client.h
+++ b/abstract_client.h
@@ -803,7 +803,7 @@
     Layer belongsToLayer() const;
     virtual bool belongsToDesktop() const;
     void invalidateLayer();
-    virtual bool isActiveFullScreen() const;
+    bool isActiveFullScreen() const;
     virtual Layer layerForDock() const;
 
     // electric border / quick tiling
diff --git a/abstract_client.cpp b/abstract_client.cpp
--- a/abstract_client.cpp
+++ b/abstract_client.cpp
@@ -1152,7 +1152,7 @@
     // according to NETWM spec implementation notes suggests
     // "focused windows having state _NET_WM_STATE_FULLSCREEN" to be on the highest layer.
     // we'll also take the screen into account
-    return ac && (ac == this || ac->screen() != screen());
+    return ac && (ac == this || ac->screen() != screen()|| ac->allMainClients().contains(const_cast<AbstractClient*>(this)));
 }
 
 #define BORDER(which) \
diff --git a/autotests/integration/x11_client_test.cpp b/autotests/integration/x11_client_test.cpp
--- a/autotests/integration/x11_client_test.cpp
+++ b/autotests/integration/x11_client_test.cpp
@@ -593,8 +593,11 @@
     // first client should be moved back to normal layer
     QCOMPARE(client->isActive(), false);
     QCOMPARE(client->isFullScreen(), true);
-    QEXPECT_FAIL("", "BUG 388310", Continue);
     QCOMPARE(client->layer(), NormalLayer);
+
+    // activating the fullscreen window again, should move it to active layer
+    workspace()->activateClient(client);
+    QTRY_COMPARE(client->layer(), ActiveLayer);
 }
 
 WAYLANDTEST_MAIN(X11ClientTest)
diff --git a/client.h b/client.h
--- a/client.h
+++ b/client.h
@@ -389,7 +389,6 @@
     void doSetSkipPager() override;
     void doSetSkipTaskbar() override;
     bool belongsToDesktop() const override;
-    bool isActiveFullScreen() const override;
     void setGeometryRestore(const QRect &geo) override;
     void updateTabGroupStates(TabGroup::States states) override;
     void doMove(int x, int y) override;
diff --git a/layers.cpp b/layers.cpp
--- a/layers.cpp
+++ b/layers.cpp
@@ -819,19 +819,4 @@
     return false;
 }
 
-bool Client::isActiveFullScreen() const
-{
-    if (AbstractClient::isActiveFullScreen()) {
-        return true;
-    }
-    if (!isFullScreen())
-        return false;
-
-    const Client* ac = dynamic_cast<Client*>(workspace()->mostRecentlyActivatedClient()); // instead of activeClient() - avoids flicker
-    // according to NETWM spec implementation notes suggests
-    // "focused windows having state _NET_WM_STATE_FULLSCREEN" to be on the highest layer.
-    // we'll also take the screen into account
-    return ac && (this->group() == ac->group());
-}
-
 } // namespace