diff --git a/src/calibre/gui2/tweak_book/spell.py b/src/calibre/gui2/tweak_book/spell.py
index c0f0f00331..7b3b690ec0 100644
--- a/src/calibre/gui2/tweak_book/spell.py
+++ b/src/calibre/gui2/tweak_book/spell.py
@@ -698,7 +698,7 @@ class WordsModel(QAbstractTableModel):
         elif col == 2:
             def key(w):
                 locale = w[1]
-                return (calibre_langcode_to_name(locale.langcode), locale.countrycode)
+                return (calibre_langcode_to_name(locale.langcode) or ''), (locale.countrycode or '')
         else:
             key = self.misspelled_text
         return key