diff --git a/python-client/wmill/wmill/client.py b/python-client/wmill/wmill/client.py
index c5c1c9b9ec..773a4c4918 100644
--- a/python-client/wmill/wmill/client.py
+++ b/python-client/wmill/wmill/client.py
@@ -911,7 +911,7 @@ def task(*args, **kwargs):
                 for i, arg in enumerate(args):
                     if i < len(params):
                         p = params[i]
-                        key = p[0]
+                        key = p
                         if key not in kwargs:
                             json[key] = arg