diff --git a/requests/models.py b/requests/models.py
index 2d83c367..49007372 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -827,6 +827,7 @@ class Response(object):
         if self.error:
             raise self.error
 
+        http_error_msg = ''
         if 300 <= self.status_code < 400 and not allow_redirects:
             http_error_msg = '%s Redirection: %s' % (self.status_code, self.reason)
 
@@ -836,6 +837,7 @@ class Response(object):
         elif 500 <= self.status_code < 600:
             http_error_msg = '%s Server Error: %s' % (self.status_code, self.reason)
 
-        http_error = HTTPError(http_error_msg)
-        http_error.response = self
-        raise http_error
+        if http_error_msg:
+            http_error = HTTPError(http_error_msg)
+            http_error.response = self
+            raise http_error