diff --git a/src/saml2/client_base.py b/src/saml2/client_base.py
index d36b9cf..fdf700b 100644
--- a/src/saml2/client_base.py
+++ b/src/saml2/client_base.py
@@ -243,7 +243,7 @@ class Base(Entity):
             try:
                 args["assertion_consumer_service_url"] = kwargs[
                     "assertion_consumer_service_url"]
-                del kwargs["assertion_consumer_service_urls"]
+                del kwargs["assertion_consumer_service_url"]
             except KeyError:
                 try:
                     args["attribute_consuming_service_index"] = str(kwargs[