diff --git a/pytorch_transformers/tokenization_utils.py b/pytorch_transformers/tokenization_utils.py
index 0bc2cbb7..9d814f70 100644
--- a/pytorch_transformers/tokenization_utils.py
+++ b/pytorch_transformers/tokenization_utils.py
@@ -641,9 +641,9 @@ class PreTrainedTokenizer(object):
         filtered_tokens = self.convert_ids_to_tokens(token_ids, skip_special_tokens=skip_special_tokens)
         text = self.convert_tokens_to_string(filtered_tokens)
 
-        if self.sep_token is not None and self.sep_token in text:
-            text = text.replace(self.cls_token, self.sep_token)
-            split_text = list(filter(lambda sentence: len(sentence) > 0, text.split(self.sep_token)))
+        if self._sep_token is not None and self._sep_token in text:
+            text = text.replace(self._cls_token, self._sep_token)
+            split_text = list(filter(lambda sentence: len(sentence) > 0, text.split(self._sep_token)))
             if clean_up_tokenization_spaces:
                 clean_text = [self.clean_up_tokenization(text) for text in split_text]
                 return clean_text