diff --git a/src/collective/dms/thesaurus/dmskeyword.py b/src/collective/dms/thesaurus/dmskeyword.py
index d67fa39..cabc876 100644
--- a/src/collective/dms/thesaurus/dmskeyword.py
+++ b/src/collective/dms/thesaurus/dmskeyword.py
@@ -74,7 +74,7 @@ class DmsKeyword(Item):
                 except KeyError:
                     continue
                 words.append(keyword.get_words_for_indexation(limit=limit-1))
-        return ' '.join(words)
+        return ' '.join([x for x in words if x])
 
     def get_keyword_tree(self, limit=5):
         thesaurus = aq_parent(self)