diff --git a/tabbox/tabbox.cpp b/tabbox/tabbox.cpp
--- a/tabbox/tabbox.cpp
+++ b/tabbox/tabbox.cpp
@@ -54,14 +54,6 @@
 #include <KConfigGroup>
 #include <KGlobalAccel>
 #include <KLocalizedString>
-#include <kkeyserver.h>
-// X11
-#include <X11/keysym.h>
-#include <X11/keysymdef.h>
-// xcb
-#include <xcb/xcb_keysyms.h>
-
-// specify externals before namespace
 
 namespace KWin
 {
@@ -910,100 +902,11 @@
     m_tabBox->grabbedKeyEvent(event);
 }
 
-struct KeySymbolsDeleter
+static bool areModKeysDepressed(const QKeySequence &seq)
 {
-    static inline void cleanup(xcb_key_symbols_t *symbols)
-    {
-        xcb_key_symbols_free(symbols);
-    }
-};
-
-/**
- * Handles alt-tab / control-tab
- **/
-static bool areKeySymXsDepressed(bool bAll, const uint keySyms[], int nKeySyms) {
-
-    qCDebug(KWIN_TABBOX) << "areKeySymXsDepressed: " << (bAll ? "all of " : "any of ") << nKeySyms;
-
-    Xcb::QueryKeymap keys;
-
-    QScopedPointer<xcb_key_symbols_t, KeySymbolsDeleter> symbols(xcb_key_symbols_alloc(connection()));
-    if (symbols.isNull() || !keys) {
+    if (seq.isEmpty()) {
         return false;
     }
-    const auto keymap = keys->keys;
-
-    for (int iKeySym = 0; iKeySym < nKeySyms; iKeySym++) {
-        uint keySymX = keySyms[ iKeySym ];
-        xcb_keycode_t *keyCodes = xcb_key_symbols_get_keycode(symbols.data(), keySymX);
-        if (!keyCodes) {
-            continue;
-        }
-        xcb_keycode_t keyCodeX = keyCodes[0];
-        free(keyCodes);
-        if (keyCodeX == XCB_NO_SYMBOL) {
-            continue;
-        }
-        int i = keyCodeX / 8;
-        char mask = 1 << (keyCodeX - (i * 8));
-
-        // Abort if bad index value,
-        if (i < 0 || i >= 32)
-            return false;
-
-        qCDebug(KWIN_TABBOX)    << iKeySym << ": keySymX=0x" << QString::number(keySymX, 16)
-                    << " i=" << i << " mask=0x" << QString::number(mask, 16)
-                    << " keymap[i]=0x" << QString::number(keymap[i], 16);
-
-        // If ALL keys passed need to be depressed,
-        if (bAll) {
-            if ((keymap[i] & mask) == 0)
-                return false;
-        } else {
-            // If we are looking for ANY key press, and this key is depressed,
-            if (keymap[i] & mask)
-                return true;
-        }
-    }
-
-    // If we were looking for ANY key press, then none was found, return false,
-    // If we were looking for ALL key presses, then all were found, return true.
-    return bAll;
-}
-
-static bool areModKeysDepressedX11(const QKeySequence &seq)
-{
-    uint rgKeySyms[10];
-    int nKeySyms = 0;
-    int mod = seq[seq.count()-1] & Qt::KeyboardModifierMask;
-
-    if (mod & Qt::SHIFT) {
-        rgKeySyms[nKeySyms++] = XK_Shift_L;
-        rgKeySyms[nKeySyms++] = XK_Shift_R;
-    }
-    if (mod & Qt::CTRL) {
-        rgKeySyms[nKeySyms++] = XK_Control_L;
-        rgKeySyms[nKeySyms++] = XK_Control_R;
-    }
-    if (mod & Qt::ALT) {
-        rgKeySyms[nKeySyms++] = XK_Alt_L;
-        rgKeySyms[nKeySyms++] = XK_Alt_R;
-    }
-    if (mod & Qt::META) {
-        // It would take some code to determine whether the Win key
-        // is associated with Super or Meta, so check for both.
-        // See bug #140023 for details.
-        rgKeySyms[nKeySyms++] = XK_Super_L;
-        rgKeySyms[nKeySyms++] = XK_Super_R;
-        rgKeySyms[nKeySyms++] = XK_Meta_L;
-        rgKeySyms[nKeySyms++] = XK_Meta_R;
-    }
-
-    return areKeySymXsDepressed(false, rgKeySyms, nKeySyms);
-}
-
-static bool areModKeysDepressedWayland(const QKeySequence &seq)
-{
     const int mod = seq[seq.count()-1] & Qt::KeyboardModifierMask;
     const Qt::KeyboardModifiers mods = input()->modifiersRelevantForGlobalShortcuts();
     if ((mod & Qt::SHIFT) && mods.testFlag(Qt::ShiftModifier)) {
@@ -1021,16 +924,6 @@
     return false;
 }
 
-static bool areModKeysDepressed(const QKeySequence& seq) {
-    if (seq.isEmpty())
-        return false;
-    if (kwinApp()->shouldUseWaylandForCompositing()) {
-        return areModKeysDepressedWayland(seq);
-    } else {
-        return areModKeysDepressedX11(seq);
-    }
-}
-
 void TabBox::navigatingThroughWindows(bool forward, const QKeySequence &shortcut, TabBoxMode mode)
 {
     if (!m_ready || isGrabbed() || !Workspace::self()->isOnCurrentHead()) {