diff --git a/autotests/CMakeLists.txt b/autotests/CMakeLists.txt
--- a/autotests/CMakeLists.txt
+++ b/autotests/CMakeLists.txt
@@ -12,12 +12,12 @@
 
 if (NOT APPLE)
     find_package(X11)
-    find_package(XCB COMPONENTS XCB)
+    find_package(XCB COMPONENTS XCB KEYSYMS)
 endif()
 
 macro(KWINDOWSYSTEM_UNIT_TESTS)
    foreach(_testname ${ARGN})
-      set(libs KF5::WindowSystem Qt5::Test Qt5::Widgets Qt5::X11Extras)
+      set(libs KF5::WindowSystem Qt5::Test Qt5::Widgets Qt5::X11Extras XCB::KEYSYMS)
       if(X11_FOUND)
          list(APPEND libs ${XCB_XCB_LIBRARY})
       endif()
diff --git a/autotests/kkeyserver_x11_unittest.cpp b/autotests/kkeyserver_x11_unittest.cpp
--- a/autotests/kkeyserver_x11_unittest.cpp
+++ b/autotests/kkeyserver_x11_unittest.cpp
@@ -21,26 +21,53 @@
 #include <QTest>
 #include "kkeyserver_x11.h"
 #include <X11/keysym.h>
+#include <xcb/xcb_keysyms.h>
+#include <QX11Info>
 
 class KKeyServerTest : public QObject
 {
     Q_OBJECT
 private Q_SLOTS:
 
+    void initTestCase()
+    {
+        m_keySymbols = xcb_key_symbols_alloc(QX11Info::connection());
+
+        // This makes me wonder why we have KKeyServer::modXShift :-)
+        QCOMPARE(XCB_MOD_MASK_SHIFT, xcb_mod_mask_t(KKeyServer::modXShift()));
+    }
+
+
+    void cleanupTestCase()
+    {
+        if (m_keySymbols) {
+            xcb_key_symbols_free(m_keySymbols);
+        }
+    }
+
     void keyQtToSymX_data()
     {
         QTest::addColumn<int>("keyQt");
         QTest::addColumn<uint>("modX");
+        QTest::addColumn<uint>("additionalState"); // set to XCB_MOD_MASK_SHIFT if shift would indeed be pressed for this shortcut
         QTest::addColumn<int>("keySymX");
 
-        QTest::newRow("a") << int(Qt::Key_A) << uint(0) << XK_A;
-        QTest::newRow("CTRL_F1") << int(Qt::ControlModifier|Qt::Key_F1) << KKeyServer::modXCtrl() << XK_F1;
-        QTest::newRow("CTRL_1") << int(Qt::ControlModifier|Qt::Key_1) << KKeyServer::modXCtrl() << XK_1;
-        QTest::newRow("CTRL_keypad_1") << int(Qt::ControlModifier|Qt::KeypadModifier|Qt::Key_1) << KKeyServer::modXCtrl() << XK_KP_1;
-        QTest::newRow("CTRL_keypad_slash") << int(Qt::ControlModifier|Qt::KeypadModifier|Qt::Key_Slash) << KKeyServer::modXCtrl() << XK_KP_Divide;
-        QTest::newRow("CTRL_ampersand") << int(Qt::ControlModifier|Qt::Key_Ampersand) << KKeyServer::modXCtrl() << XK_ampersand;
-        QTest::newRow("ALT_SHIFT_right") << int(Qt::AltModifier|Qt::ShiftModifier|Qt::Key_Right) << (KKeyServer::modXAlt() | KKeyServer::modXShift()) << XK_Right;
-        QTest::newRow("META_SHIFT_print") << int(Qt::MetaModifier|Qt::ShiftModifier|Qt::Key_Print) << (KKeyServer::modXMeta() | KKeyServer::modXShift()) << XK_Print;
+        const uint numLock = KKeyServer::modXNumLock();
+
+        // Before adding any testcase below, check what `kcmshell5 keys` records, to make sure it matches
+        QTest::newRow("a") << int(Qt::Key_A) << uint(0) << numLock << XK_A;
+        QTest::newRow("CTRL_F1") << int(Qt::ControlModifier|Qt::Key_F1) << KKeyServer::modXCtrl() << numLock << XK_F1;
+        QTest::newRow("CTRL_1") << int(Qt::ControlModifier|Qt::Key_1) << KKeyServer::modXCtrl() << numLock << XK_1;
+        QTest::newRow("CTRL_keypad_1") << int(Qt::ControlModifier|Qt::KeypadModifier|Qt::Key_1) << KKeyServer::modXCtrl() << numLock << XK_KP_1;
+        QTest::newRow("CTRL_keypad_slash") << int(Qt::ControlModifier|Qt::KeypadModifier|Qt::Key_Slash) << KKeyServer::modXCtrl() << numLock << XK_KP_Divide;
+        QTest::newRow("CTRL_SHIFT_keypad_end") << int(Qt::ControlModifier|Qt::ShiftModifier|Qt::KeypadModifier|Qt::Key_End) << (KKeyServer::modXCtrl()|KKeyServer::modXShift()) << numLock << XK_KP_End;
+        QTest::newRow("CTRL_keypad_end_no_numlock") << int(Qt::ControlModifier|Qt::KeypadModifier|Qt::Key_End) << (KKeyServer::modXCtrl()) << uint(0) << XK_KP_End;
+        QTest::newRow("CTRL_ampersand") << int(Qt::ControlModifier|Qt::Key_Ampersand) << KKeyServer::modXCtrl() << uint(XCB_MOD_MASK_SHIFT|numLock) << XK_ampersand;
+        QTest::newRow("ALT_SHIFT_right") << int(Qt::AltModifier|Qt::ShiftModifier|Qt::Key_Right) << (KKeyServer::modXAlt() | KKeyServer::modXShift()) << numLock << XK_Right;
+        QTest::newRow("CTRL_SHIFT_right") << int(Qt::ControlModifier|Qt::ShiftModifier|Qt::Key_Right) << (KKeyServer::modXCtrl() | KKeyServer::modXShift()) << numLock << XK_Right;
+        QTest::newRow("META_SHIFT_print") << int(Qt::MetaModifier|Qt::ShiftModifier|Qt::Key_Print) << (KKeyServer::modXMeta() | KKeyServer::modXShift()) << numLock << XK_Print;
+        QTest::newRow("ALT_Tab") << int(Qt::AltModifier|Qt::Key_Tab) << (KKeyServer::modXAlt()) << numLock << XK_Tab;
+        QTest::newRow("ALT_Shift_Tab") << int(Qt::AltModifier|Qt::ShiftModifier|Qt::Key_Tab) << (KKeyServer::modXAlt() | KKeyServer::modXShift()) << numLock << XK_Tab;
     }
 
     void keyQtToSymX()
@@ -50,7 +77,7 @@
         QFETCH(int, keySymX);
         int sym;
         QVERIFY(KKeyServer::keyQtToSymX(keyQt, &sym));
-        QCOMPARE(sym, keySymX);
+        QCOMPARE(QString::number(sym, 16), QString::number(keySymX, 16));
         uint mod;
         QVERIFY(KKeyServer::keyQtToModX(keyQt, &mod));
         QCOMPARE(mod, modX);
@@ -68,12 +95,45 @@
         QFETCH(int, keySymX);
         int keyCodeQt;
 
-        //qDebug() << "modX=" << modX << "keySymX=0x" << QString::number(keySymX, 16);
+        //qDebug() << "modX=" << modX << "keySymX=0x" << QString::number(keySymX, 16) << "keyQt=0x" << QString::number(keyQt, 16);
 
         QVERIFY(KKeyServer::symXModXToKeyQt(keySymX, modX, &keyCodeQt));
         QCOMPARE(keyCodeQt, keyQt);
     }
 
+    void decodeXcbEvent_data()
+    {
+        keyQtToSymX_data();
+    }
+
+    void decodeXcbEvent()
+    {
+        QFETCH(int, keyQt);
+        QFETCH(uint, modX);
+        QFETCH(uint, additionalState);
+        QFETCH(int, keySymX);
+
+        xcb_keycode_t *keyCodes = xcb_key_symbols_get_keycode(m_keySymbols, keySymX);
+        QVERIFY(keyCodes);
+        const xcb_keycode_t keyCodeX = keyCodes[0];
+        QVERIFY(keyCodeX != XCB_NO_SYMBOL);
+        free(keyCodes);
+
+        xcb_key_press_event_t event{ XCB_KEY_PRESS, keyCodeX, 0, 0 /*time*/, 0 /*root*/, 0 /*event*/, 0 /*child*/, 0 /*root_x*/, 0 /*root_y*/, 0 /*event_x*/, 0 /*event_y*/,
+            uint16_t(modX | additionalState), 0 /*same_screen*/, 0 /*pad0*/ };
+
+        int decodedKeyQt;
+        const bool ok = KKeyServer::xcbKeyPressEventToQt(&event, &decodedKeyQt);
+        QVERIFY(ok);
+        if (decodedKeyQt != keyQt) {
+            qDebug() << "given modX=" << modX << "keySymX=0x" << QString::number(keySymX, 16) << "I expected keyQt=0x" << QString::number(keyQt, 16) << QKeySequence(keyQt).toString() << "got" << QString::number(decodedKeyQt, 16) << QKeySequence(decodedKeyQt).toString();
+        }
+        QCOMPARE(decodedKeyQt, keyQt);
+    }
+
+private:
+    xcb_key_symbols_t *m_keySymbols;
+
 };
 
 QTEST_MAIN(KKeyServerTest)
diff --git a/src/platforms/xcb/kkeyserver.cpp b/src/platforms/xcb/kkeyserver.cpp
--- a/src/platforms/xcb/kkeyserver.cpp
+++ b/src/platforms/xcb/kkeyserver.cpp
@@ -964,10 +964,7 @@
         else
             keySymX = keySym1;
     } else {
-        if ((e->state & XCB_MOD_MASK_SHIFT))
-            keySymX = keySym1;
-        else
-            keySymX = keySym0;
+        keySymX = keySym0;
     }
 
     bool ok = KKeyServer::symXModXToKeyQt(keySymX, keyModX, keyQt);