diff --git a/zulip/zulip/__init__.py b/zulip/zulip/__init__.py
index 67faadb..6853cc3 100644
--- a/zulip/zulip/__init__.py
+++ b/zulip/zulip/__init__.py
@@ -337,6 +337,7 @@ class Client(object):
             raise RuntimeError("api_key or email not specified and file %s does not exist"
                                % (config_file,))
 
+        assert(api_key is not None and email is not None)
         self.api_key = api_key
         self.email = email
         self.verbose = verbose