diff --git a/requests/__init__.py b/requests/__init__.py
index 05c9b82c..eb6639f9 100644
--- a/requests/__init__.py
+++ b/requests/__init__.py
@@ -28,6 +28,6 @@ from .api import request, get, head, post, patch, put, delete
 from .sessions import session
 from .status_codes import codes
 from .exceptions import (
-    RequestException, AuthenticationError, Timeout, URLRequired,
-    TooManyRedirects, HTTPError
+    RequestException, Timeout, URLRequired,
+    TooManyRedirects, HTTPError, ConnectionError
 )
diff --git a/requests/models.py b/requests/models.py
index 3a30aa03..3b711cf5 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -444,7 +444,7 @@ class Response(object):
         self.cookies = {}
 
         #: Dictionary of configurations for this request.
-        self.config = None
+        self.config = {}
 
 
     def __repr__(self):