diff --git a/scripts/hpp_genxr.py b/scripts/hpp_genxr.py
index ce419b0..23e1d3d 100644
--- a/scripts/hpp_genxr.py
+++ b/scripts/hpp_genxr.py
@@ -36,7 +36,7 @@ from xrconventions import OpenXRConventions
 from data import EXCLUDED_EXTENSIONS


-def makeREstring(strings: Iterable[str], default: typing.Optional[str] = None) -> str:
+def makeREstring(strings, default: typing.Optional[str] = None) -> str:
     """Turn a list of strings into a regexp string matching exactly those strings."""
     if strings or default is None:
         return f"^({'|'.join(re.escape(s) for s in strings)})$"