diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.cpp b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
index 260fb46..5fb7457 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
@@ -950,21 +950,22 @@
 
     quint32 keycode = event->nativeScanCode();
     xkb_keysym_t sym = xkb_state_key_get_one_sym(kb_state, keycode);
     if (sym == XKB_KEY_NoSymbol) {
         xkb_state_unref(kb_state);
         return QList<int>();
     }
 
     QList<int> result;
     int baseQtKey = keysymToQtKey(sym, modifiers, lookupString(kb_state, keycode));
-    result += (baseQtKey + modifiers); // The base key is _always_ valid, of course
+    if (baseQtKey)
+        result += (baseQtKey + modifiers);
 
     xkb_mod_index_t shiftMod = xkb_keymap_mod_get_index(xkb_keymap, "Shift");
     xkb_mod_index_t altMod = xkb_keymap_mod_get_index(xkb_keymap, "Alt");
     xkb_mod_index_t controlMod = xkb_keymap_mod_get_index(xkb_keymap, "Control");
 
     Q_ASSERT(shiftMod < 32);
     Q_ASSERT(altMod < 32);
     Q_ASSERT(controlMod < 32);
 
     xkb_mod_mask_t depressed;