diff --git a/gramps/gui/editors/displaytabs/citationrefmodel.py b/gramps/gui/editors/displaytabs/citationrefmodel.py
index 3b4a6e093a..c9a841fb5f 100644
--- a/gramps/gui/editors/displaytabs/citationrefmodel.py
+++ b/gramps/gui/editors/displaytabs/citationrefmodel.py
@@ -39,7 +39,9 @@
 # -------------------------------------------------------------------------
 class CitationRefModel(Gtk.ListStore):
     def __init__(self, citation_list, db):
-        Gtk.ListStore.__init__(self, str, str, str, str, str, str, str, bool, str, str, str)
+        Gtk.ListStore.__init__(
+            self, str, str, str, str, str, str, str, bool, str, str, str
+        )
         self.db = db
         dbgsfh = self.db.get_source_from_handle
         for handle in citation_list: