diff --git a/jeeves/core/objects.py b/jeeves/core/objects.py
index ae12ac3..49b0e4b 100644
--- a/jeeves/core/objects.py
+++ b/jeeves/core/objects.py
@@ -24,7 +24,7 @@ class Task(BaseObject):
 
 class Argument(BaseObject):
     name: Text
-    default: Any
+    default: Optional[Any] = None
     type: Text = "text"
     required: bool = False