diff -up firefox-80.0/widget/gtk/nsWindow.cpp.1196777 firefox-80.0/widget/gtk/nsWindow.cpp
--- firefox-80.0/widget/gtk/nsWindow.cpp.1196777	2020-08-18 09:47:18.662833910 +0200
+++ firefox-80.0/widget/gtk/nsWindow.cpp	2020-08-18 09:48:19.437478136 +0200
@@ -158,7 +158,8 @@ const gint kEvents =
     GDK_EXPOSURE_MASK | GDK_STRUCTURE_MASK | GDK_VISIBILITY_NOTIFY_MASK |
     GDK_ENTER_NOTIFY_MASK | GDK_LEAVE_NOTIFY_MASK | GDK_BUTTON_PRESS_MASK |
     GDK_BUTTON_RELEASE_MASK | GDK_SMOOTH_SCROLL_MASK | GDK_TOUCH_MASK |
-    GDK_SCROLL_MASK | GDK_POINTER_MOTION_MASK | GDK_PROPERTY_CHANGE_MASK;
+    GDK_SCROLL_MASK | GDK_POINTER_MOTION_MASK | GDK_PROPERTY_CHANGE_MASK |
+    GDK_FOCUS_CHANGE_MASK;
 
 #if !GTK_CHECK_VERSION(3, 22, 0)
 typedef enum {