diff --git a/asdf/_asdf.py b/asdf/_asdf.py
index 8eb220b3e..434733f87 100644
--- a/asdf/_asdf.py
+++ b/asdf/_asdf.py
@@ -57,7 +57,6 @@ def __init__(
         extensions=None,
         version=None,
         ignore_unrecognized_tag=False,
-        ignore_implicit_conversion=NotSet,
         memmap=False,
         lazy_load=True,
         custom_schema=None,