diff --git a/dockbarx/dockbar.py b/dockbarx/dockbar.py
index 51ae10b..6115dee 100644
--- a/dockbarx/dockbar.py
+++ b/dockbarx/dockbar.py
@@ -875,6 +875,8 @@ def __on_active_window_changed(self, screen, previous_active_window):
             group.set_active_window(None)
         # Activate new windowbutton
         active_window = screen.get_active_window()
+        if active_window == None:
+            active_window = previous_active_window
         if active_window in self.windows:
             active_group_name = self.windows[active_window]
             active_group = self.groups[active_group_name]