diff --git a/tests/test_trioisms.py b/tests/test_trioisms.py
index 6aaf20b3..431730f3 100644
--- a/tests/test_trioisms.py
+++ b/tests/test_trioisms.py
@@ -117,7 +117,6 @@ def test_acm_embedded_nursery_propagates_enter_err(
         async with (
             trio.open_nursery() as tn,
             tractor.trionics.maybe_raise_from_masking_exc(
-                tn=tn,
                 unmask_from=(
                     (trio.Cancelled,) if unmask_from_canc
                     else ()
diff --git a/tractor/trionics/_taskc.py b/tractor/trionics/_taskc.py
index fb743bbc..4e336b59 100644
--- a/tractor/trionics/_taskc.py
+++ b/tractor/trionics/_taskc.py
@@ -65,7 +65,6 @@ def find_masked_excs(
 #
 @acm
 async def maybe_raise_from_masking_exc(
-    tn: trio.Nursery|None = None,
     unmask_from: (
         BaseException|
         tuple[BaseException]