diff --git a/src/transformers/configuration_utils.py b/src/transformers/configuration_utils.py
index d8cd0fe3e9fe..407f5d4dd13e 100644
--- a/src/transformers/configuration_utils.py
+++ b/src/transformers/configuration_utils.py
@@ -20,6 +20,7 @@
 import json
 import logging
 import os
+import sys
 from typing import Dict, Optional, Tuple
 
 from .file_utils import CONFIG_NAME, cached_path, hf_bucket_url, is_remote_url
@@ -98,15 +99,19 @@ def __init__(self, **kwargs):
                 logger.error("Can't set {} with value {} for {}".format(key, value, self))
                 raise err
 
-    def save_pretrained(self, save_directory):
-        """
-        Save a configuration object to the directory `save_directory`, so that it
-        can be re-loaded using the :func:`~transformers.PretrainedConfig.from_pretrained` class method.
+    @property
+    def num_labels(self):
+        return self._num_labels
 
-        Args:
-            save_directory (:obj:`string`):
-                Directory where the configuration JSON file will be saved.
-        """
+    @num_labels.setter
+    def num_labels(self, num_labels):
+        self._num_labels = num_labels
+        self.id2label = {i: "LABEL_{}".format(i) for i in range(self.num_labels)}
+        self.id2label = dict((int(key), value) for key, value in self.id2label.items())
+        self.label2id = dict(zip(self.id2label.values(), self.id2label.keys()))
+        self.label2id = dict((key, int(value)) for key, value in self.label2id.items())
+
+    def save_pretrained(self, save_directory):
         assert os.path.isdir(
             save_directory
         ), "Saving path should be a directory where the model and configuration can be saved"
@@ -223,8 +228,6 @@ def get_config_dict(
                 local_files_only=local_files_only,
             )
             # Load config dict
-            if resolved_config_file is None:
-                raise EnvironmentError
             config_dict = cls._dict_from_json_file(resolved_config_file)
 
         except EnvironmentError: