diff --git a/src/calibre/ebooks/oeb/polish/spell.py b/src/calibre/ebooks/oeb/polish/spell.py
index b07ea6f8f6..8ffe264bcb 100644
--- a/src/calibre/ebooks/oeb/polish/spell.py
+++ b/src/calibre/ebooks/oeb/polish/spell.py
@@ -94,7 +94,7 @@ def add_words(text, node, words, file_name, locale, node_item):
         p = patterns()
         is_fr = locale.langcode == 'fra'
         for word in candidates:
-            sword = p.sanitize_invisible_pat.sub('', word)
+            sword = p.sanitize_invisible_pat.sub('', word).strip()
             elided_prefix = ''
             if is_fr:
                 m = p.fr_elision_pat.match(sword)