diff --git a/streamz/core.py b/streamz/core.py
index f381b632..d5f3579d 100644
--- a/streamz/core.py
+++ b/streamz/core.py
@@ -157,8 +157,9 @@ def register_api(cls, modifier=identity, attribute_name=None):
         """
         def _(func):
             @functools.wraps(func)
-            def wrapped(*args, **kwargs):
-                return func(*args, **kwargs)
+            def wrapped(self, *args, **kwargs):
+                fn = type(name, (type(self), func), dict(func.__dict__))
+                return fn(self, *args, **kwargs)
             name = attribute_name if attribute_name else func.__name__
             setattr(cls, name, modifier(wrapped))
             return func