diff -up firefox-64.0/widget/gtk/nsGtkKeyUtils.cpp.old firefox-64.0/widget/gtk/nsGtkKeyUtils.cpp
--- firefox-64.0/widget/gtk/nsGtkKeyUtils.cpp.old	2018-12-05 13:17:51.147655931 +0100
+++ firefox-64.0/widget/gtk/nsGtkKeyUtils.cpp	2018-12-05 13:18:57.989282016 +0100
@@ -590,7 +590,7 @@ seat_handle_capabilities(void *data, str
 {
     static wl_keyboard *keyboard = nullptr;
 
-    if (caps & WL_SEAT_CAPABILITY_KEYBOARD) {
+    if ((caps & WL_SEAT_CAPABILITY_KEYBOARD) && !keyboard) {
         keyboard = wl_seat_get_keyboard(seat);
         wl_keyboard_add_listener(keyboard, &keyboard_listener, nullptr);
     } else if (keyboard && !(caps & WL_SEAT_CAPABILITY_KEYBOARD)) {