diff --git a/docker/client.py b/docker/client.py
index 34f8e990..7eccba30 100644
--- a/docker/client.py
+++ b/docker/client.py
@@ -901,7 +901,7 @@ class Client(requests.Session):
                     # auth_config needs to be a dict in the format used by
                     # auth.py username , password, serveraddress, email
                     headers['X-Registry-Auth'] = auth.encode_header(
-                        auth_config)
+                        authcfg)
             else:
                 headers['X-Registry-Auth'] = auth.encode_header(auth_config)