diff --git a/tractor/_actor.py b/tractor/_actor.py
index cb9dc7b..f8f2bdd 100644
--- a/tractor/_actor.py
+++ b/tractor/_actor.py
@@ -9,7 +9,7 @@ import importlib.util
 import inspect
 import uuid
 import typing
-from typing import Dict, List, Tuple, Any, Optional
+from typing import Dict, List, Tuple, Any, Optional, Union
 from types import ModuleType
 import sys
 import os
@@ -48,7 +48,9 @@ async def _invoke(
     chan: Channel,
     func: typing.Callable,
     kwargs: Dict[str, Any],
-    task_status: TaskStatus[trio.CancelScope] = trio.TASK_STATUS_IGNORED,
+    task_status: TaskStatus[
+        Union[trio.CancelScope, BaseException]
+    ] = trio.TASK_STATUS_IGNORED,
 ):
     """Invoke local func and deliver result(s) over provided channel.
     """
@@ -155,6 +157,7 @@ async def _invoke(
         if cs is None:
             # error is from above code not from rpc invocation
             task_status.started(err)
+
     finally:
         # RPC task bookeeping
         try:
diff --git a/tractor/_portal.py b/tractor/_portal.py
index 6c026f8..9ad4c2f 100644
--- a/tractor/_portal.py
+++ b/tractor/_portal.py
@@ -204,8 +204,8 @@ class Portal:
         fn_name: Optional[str] = None,
         **kwargs
     ) -> Any:
-        """Submit a remote function to be scheduled and run by actor,
-        wrap and return its (stream of) result(s).
+        """Submit a remote function to be scheduled and run by actor, in
+        a new task, wrap and return its (stream of) result(s).
 
         This is a blocking call and returns either a value from the
         remote rpc task or a local async generator instance.
diff --git a/tractor/_streaming.py b/tractor/_streaming.py
index 9ed0f14..e683216 100644
--- a/tractor/_streaming.py
+++ b/tractor/_streaming.py
@@ -37,7 +37,7 @@ def current_context():
 
 
 def stream(func):
-    """Mark an async function as a streaming routine.
+    """Mark an async function as a streaming routine with ``@stream``.
     """
     func._tractor_stream_function = True
     sig = inspect.signature(func)
diff --git a/tractor/msg.py b/tractor/msg.py
index 4184333..5b343b6 100644
--- a/tractor/msg.py
+++ b/tractor/msg.py
@@ -3,7 +3,7 @@ Messaging pattern APIs and helpers.
 """
 import inspect
 import typing
-from typing import Dict, Any, Set, Union, Callable
+from typing import Dict, Any, Set, Callable
 from functools import partial
 from async_generator import aclosing
 
@@ -90,7 +90,7 @@ def modify_subs(topics2ctxs, topics, ctx):
 
 
 _pub_state: Dict[str, dict] = {}
-_pubtask2lock: Dict[str, dict] = {}
+_pubtask2lock: Dict[str, trio.StrictFIFOLock] = {}
 
 
 def pub(
@@ -184,7 +184,7 @@ def pub(
     if wrapped is None:
         return partial(pub, tasks=tasks)
 
-    task2lock: Dict[Union[str, None], trio.StrictFIFOLock] = {}
+    task2lock: Dict[str, trio.StrictFIFOLock] = {}
 
     for name in tasks:
         task2lock[name] = trio.StrictFIFOLock()