diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -233,7 +233,6 @@
         SHM
         GLX
         CURSOR
-    OPTIONAL_COMPONENTS
         ICCCM
 )
 set_package_properties(XCB PROPERTIES TYPE REQUIRED)
@@ -569,6 +568,7 @@
     XCB::KEYSYMS
     XCB::SHM
     XCB::GLX
+    XCB::ICCCM
 )
 
 set(kwin_WAYLAND_LIBS
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
@@ -51,6 +51,7 @@
     void testFullscreenLayerWithActiveWaylandWindow();
     void testFocusInWithWaylandLastActiveWindow();
     void testX11WindowId();
+    void testCaptionWmName();
 };
 
 void X11ClientTest::initTestCase()
@@ -376,5 +377,27 @@
     xcb_flush(c.data());
 }
 
+void X11ClientTest::testCaptionWmName()
+{
+    // this test verifies that a caption set through WM_NAME is read correctly
+
+    // open glxgears as that one only uses WM_NAME
+    QSignalSpy clientAddedSpy(workspace(), &Workspace::clientAdded);
+    QVERIFY(clientAddedSpy.isValid());
+
+    QProcess glxgears;
+    glxgears.start(QStringLiteral("glxgears"));
+    QVERIFY(glxgears.waitForStarted());
+
+    QVERIFY(clientAddedSpy.wait());
+    QCOMPARE(clientAddedSpy.count(), 1);
+    QCOMPARE(workspace()->clientList().count(), 1);
+    Client *glxgearsClient = workspace()->clientList().first();
+    QCOMPARE(glxgearsClient->caption(), QStringLiteral("glxgears"));
+
+    glxgears.terminate();
+    QVERIFY(glxgears.waitForFinished());
+}
+
 WAYLANDTEST_MAIN(X11ClientTest)
 #include "x11_client_test.moc"
diff --git a/client.cpp b/client.cpp
--- a/client.cpp
+++ b/client.cpp
@@ -55,6 +55,7 @@
 // XLib
 #include <X11/Xutil.h>
 #include <fixx11h.h>
+#include <xcb/xcb_icccm.h>
 // system
 #include <unistd.h>
 #include <signal.h>
@@ -1414,12 +1415,30 @@
     setCaption(readName());
 }
 
+static inline QString readNameProperty(xcb_window_t w, xcb_atom_t atom)
+{
+    const auto cookie = xcb_icccm_get_text_property_unchecked(connection(), w, atom);
+    xcb_icccm_get_text_property_reply_t reply;
+    if (xcb_icccm_get_wm_name_reply(connection(), cookie, &reply, nullptr)) {
+        QString retVal;
+        if (reply.encoding == atoms->utf8_string) {
+            retVal = QString::fromUtf8(QByteArray(reply.name, reply.name_len));
+        } else if (reply.encoding == XCB_ATOM_STRING) {
+            retVal = QString::fromLocal8Bit(QByteArray(reply.name, reply.name_len));
+        }
+        xcb_icccm_get_text_property_reply_wipe(&reply);
+        return retVal.simplified();
+    }
+    return QString();
+}
+
 QString Client::readName() const
 {
     if (info->name() && info->name()[0] != '\0')
         return QString::fromUtf8(info->name()).simplified();
-    else
-        return KWindowSystem::readNameProperty(window(), XCB_ATOM_WM_NAME).simplified();
+    else {
+        return readNameProperty(window(), XCB_ATOM_WM_NAME);
+    }
 }
 
 // The list is taken from http://www.unicode.org/reports/tr9/ (#154840)
@@ -1511,7 +1530,7 @@
     if (info->iconName() && info->iconName()[0] != '\0')
         s = QString::fromUtf8(info->iconName());
     else
-        s = KWindowSystem::readNameProperty(window(), XCB_ATOM_WM_ICON_NAME);
+        s = readNameProperty(window(), XCB_ATOM_WM_ICON_NAME);
     if (s != cap_iconic) {
         bool was_set = !cap_iconic.isEmpty();
         cap_iconic = s;