diff --git a/stdlib/@tests/stubtest_allowlists/py315.txt b/stdlib/@tests/stubtest_allowlists/py315.txt
index b93738f041ec..4c9f3292ff5d 100644
--- a/stdlib/@tests/stubtest_allowlists/py315.txt
+++ b/stdlib/@tests/stubtest_allowlists/py315.txt
@@ -8,7 +8,6 @@ _frozen_importlib_external.SourceLoader.source_to_code
 dataclasses.MISSING
 dataclasses._MISSING_TYPE
 dataclasses.field
-mailbox._ProxyFile.__class_getitem__
 
 # =============================================================
 # Allowlist entries that cannot or should not be fixed; >= 3.15
diff --git a/stdlib/mailbox.pyi b/stdlib/mailbox.pyi
index 4215120a5753..7f3024094b43 100644
--- a/stdlib/mailbox.pyi
+++ b/stdlib/mailbox.pyi
@@ -294,7 +294,8 @@ class _ProxyFile:
     def flush(self) -> None: ...
     @property
     def closed(self) -> bool: ...
-    def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
+    if sys.version_info < (3, 15):
+        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class _PartialFile(_ProxyFile):
     def __init__(self, f: _GetFileReturn, start: int | None = None, stop: int | None = None) -> None: ...