diff --git a/stdlib/@python2/_io.pyi b/stdlib/@python2/_io.pyi
index 3c1eab23b..3671bbd21 100644
--- a/stdlib/@python2/_io.pyi
+++ b/stdlib/@python2/_io.pyi
@@ -35,7 +35,7 @@ class _IOBase(BinaryIO):
     # The parameter type of writelines[s]() is determined by that of write():
     def writelines(self, lines: Iterable[bytes]) -> None: ...
     # The return type of readline[s]() and next() is determined by that of read():
-    def readline(self, limit: int = ...) -> bytes: ...
+    def readline(self, limit: int | None = ...) -> bytes: ...
     def readlines(self, hint: int = ...) -> list[bytes]: ...
     def next(self) -> bytes: ...
     # These don't actually exist but we need to pretend that it does