diff --git a/src/calibre/gui2/actions/virtual_library.py b/src/calibre/gui2/actions/virtual_library.py
index 20655563a6..596b697528 100644
--- a/src/calibre/gui2/actions/virtual_library.py
+++ b/src/calibre/gui2/actions/virtual_library.py
@@ -19,7 +19,7 @@ class VirtualLibraryAction(InterfaceAction):
     action_type = 'current'
     action_add_menu = True
     popup_type = QToolButton.InstantPopup
-    dont_add_to = frozenset(['context-menu-device', 'menubar-device'])
+    dont_add_to = frozenset(('context-menu-device', 'menubar-device'))
 
     def genesis(self):
         self.menu = m = self.qaction.menu()