diff --git a/src/calibre/customize/conversion.py b/src/calibre/customize/conversion.py
index 50bceb4def..fe0d563206 100644
--- a/src/calibre/customize/conversion.py
+++ b/src/calibre/customize/conversion.py
@@ -257,7 +257,7 @@ class InputFormatPlugin(Plugin):
         pass
 
     def gui_configuration_widget(self, parent, get_option_by_name,
-            get_option_help, db, book_id):
+            get_option_help, db, book_id=None):
         '''
         Called to create the widget used for configuring this plugin in the
         calibre GUI. The widget must be an instance of the PluginWidget class.
@@ -351,7 +351,7 @@ class OutputFormatPlugin(Plugin):
         pass
 
     def gui_configuration_widget(self, parent, get_option_by_name,
-            get_option_help, db, book_id):
+            get_option_help, db, book_id=None):
         '''
         Called to create the widget used for configuring this plugin in the
         calibre GUI. The widget must be an instance of the PluginWidget class.