diff --git a/autotests/integration/window_rules_test.cpp b/autotests/integration/window_rules_test.cpp
--- a/autotests/integration/window_rules_test.cpp
+++ b/autotests/integration/window_rules_test.cpp
@@ -47,6 +47,7 @@
     void cleanup();
     void testApplyInitialMaximizeVert_data();
     void testApplyInitialMaximizeVert();
+    void testWindowClassChange();
 };
 
 void WindowRuleTest::initTestCase()
@@ -165,6 +166,85 @@
     QVERIFY(windowClosedSpy.wait());
 }
 
+void WindowRuleTest::testWindowClassChange()
+{
+    KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
+    config->group("General").writeEntry("count", 1);
+
+    auto group = config->group("1");
+    group.writeEntry("above", true);
+    group.writeEntry("aboverule", 2);
+    group.writeEntry("wmclass", "org.kde.foo");
+    group.writeEntry("wmclasscomplete", false);
+    group.writeEntry("wmclassmatch", 1);
+    group.sync();
+
+    RuleBook::self()->setConfig(config);
+    workspace()->slotReconfigure();
+
+    // create the test window
+    QScopedPointer<xcb_connection_t, XcbConnectionDeleter> c(xcb_connect(nullptr, nullptr));
+    QVERIFY(!xcb_connection_has_error(c.data()));
+
+    xcb_window_t w = xcb_generate_id(c.data());
+    const QRect windowGeometry = QRect(0, 0, 10, 20);
+    const uint32_t values[] = {
+        XCB_EVENT_MASK_ENTER_WINDOW |
+        XCB_EVENT_MASK_LEAVE_WINDOW
+    };
+    xcb_create_window(c.data(), XCB_COPY_FROM_PARENT, w, rootWindow(),
+                      windowGeometry.x(),
+                      windowGeometry.y(),
+                      windowGeometry.width(),
+                      windowGeometry.height(),
+                      0, XCB_WINDOW_CLASS_INPUT_OUTPUT, XCB_COPY_FROM_PARENT, XCB_CW_EVENT_MASK, values);
+    xcb_size_hints_t hints;
+    memset(&hints, 0, sizeof(hints));
+    xcb_icccm_size_hints_set_position(&hints, 1, windowGeometry.x(), windowGeometry.y());
+    xcb_icccm_size_hints_set_size(&hints, 1, windowGeometry.width(), windowGeometry.height());
+    xcb_icccm_set_wm_normal_hints(c.data(), w, &hints);
+    xcb_icccm_set_wm_class(c.data(), w, 23, "org.kde.bar\0org.kde.bar");
+
+    NETWinInfo info(c.data(), w, rootWindow(), NET::WMAllProperties, NET::WM2AllProperties);
+    info.setWindowType(NET::Normal);
+    xcb_map_window(c.data(), w);
+    xcb_flush(c.data());
+
+    QSignalSpy windowCreatedSpy(workspace(), &Workspace::clientAdded);
+    QVERIFY(windowCreatedSpy.isValid());
+    QVERIFY(windowCreatedSpy.wait());
+    Client *client = windowCreatedSpy.last().first().value<Client*>();
+    QVERIFY(client);
+    QVERIFY(client->isDecorated());
+    QVERIFY(!client->hasStrut());
+    QVERIFY(!client->isHiddenInternal());
+    QVERIFY(!client->readyForPainting());
+    QMetaObject::invokeMethod(client, "setReadyForPainting");
+    QVERIFY(client->readyForPainting());
+    QVERIFY(!client->surface());
+    QSignalSpy surfaceChangedSpy(client, &Toplevel::surfaceChanged);
+    QVERIFY(surfaceChangedSpy.isValid());
+    QVERIFY(surfaceChangedSpy.wait());
+    QVERIFY(client->surface());
+    QCOMPARE(client->keepAbove(), false);
+
+    // now change class
+    QSignalSpy windowClassChangedSpy{client, &Client::windowClassChanged};
+    QVERIFY(windowClassChangedSpy.isValid());
+    xcb_icccm_set_wm_class(c.data(), w, 23, "org.kde.foo\0org.kde.foo");
+    xcb_flush(c.data());
+    QVERIFY(windowClassChangedSpy.wait());
+    QCOMPARE(client->keepAbove(), true);
+
+    // destroy window
+    QSignalSpy windowClosedSpy(client, &Client::windowClosed);
+    QVERIFY(windowClosedSpy.isValid());
+    xcb_unmap_window(c.data(), w);
+    xcb_destroy_window(c.data(), w);
+    xcb_flush(c.data());
+    QVERIFY(windowClosedSpy.wait());
+}
+
 }
 
 WAYLANDTEST_MAIN(KWin::WindowRuleTest)
diff --git a/manage.cpp b/manage.cpp
--- a/manage.cpp
+++ b/manage.cpp
@@ -132,6 +132,8 @@
     setupWindowRules(false);
     setCaption(cap_normal, true);
 
+    connect(this, &Client::windowClassChanged, this, &Client::evaluateWindowRules);
+
     if (Xcb::Extensions::self()->isShapeAvailable())
         xcb_shape_select_input(connection(), window(), true);
     detectShape(window());