diff --git a/spacy/language.py b/spacy/language.py
index 739e7665d..cacce85c7 100644
--- a/spacy/language.py
+++ b/spacy/language.py
@@ -560,9 +560,9 @@ class Language(object):
             elif len(old_refs) == 0:
                 self.vocab.strings._cleanup_stale_strings()
                 nr_seen = 0
-        # Last batch can be not garbage collected and we cannot know it — last
-        # doc still here. Not erase that strings — just extend with original
-        # content
+        # We can't know which strings from the last batch have really expired.
+        # So we don't erase the strings — we just extend with the original
+        # content.
         for string in original_strings_data:
             self.vocab.strings.add(string)