diff --git a/endpoints/api/__init__.py b/endpoints/api/__init__.py
index 85c3c878d..5b5253ff6 100644
--- a/endpoints/api/__init__.py
+++ b/endpoints/api/__init__.py
@@ -53,6 +53,10 @@ class InvalidRequest(ApiException):
   def __init__(self, error_description, payload=None):
     ApiException.__init__(self, 'invalid_request', 400, error_description, payload)
 
+class InvalidResponse(ApiException):
+  def __init__(self, error_description, payload=None):
+    ApiException.__init__(self, 'invalid_response', 400, error_description, payload)
+
 
 class InvalidToken(ApiException):
   def __init__(self, error_description, payload=None):
@@ -173,7 +177,7 @@ def path_param(name, description):
   def add_param(func):
     if not func:
       return func
-      
+
     if '__api_path_params' not in dir(func):
       func.__api_path_params = {}
     func.__api_path_params[name] = {
@@ -293,7 +297,7 @@ def require_fresh_login(func):
 
     if not user.password_hash or last_login >= valid_span:
       return func(*args, **kwargs)
-    
+
     raise FreshLoginRequired()
   return wrapped