diff --git a/stubs/pyRFC3339/METADATA.toml b/stubs/pyRFC3339/METADATA.toml
index bad265e4f..c3a335e96 100644
--- a/stubs/pyRFC3339/METADATA.toml
+++ b/stubs/pyRFC3339/METADATA.toml
@@ -1 +1,4 @@
 version = "1.1"
+
+[tool.stubtest]
+ignore_missing_stub = false
diff --git a/stubs/pyRFC3339/pyrfc3339/utils.pyi b/stubs/pyRFC3339/pyrfc3339/utils.pyi
index 54588acf7..d71f3c94e 100644
--- a/stubs/pyRFC3339/pyrfc3339/utils.pyi
+++ b/stubs/pyRFC3339/pyrfc3339/utils.pyi
@@ -1,10 +1,13 @@
+from _typeshed import Self
 from datetime import datetime, timedelta, tzinfo
+from typing import Any
 
 class FixedOffset(tzinfo):
     def __init__(self, hours: float, minutes: float) -> None: ...
     def dst(self, dt: datetime | None) -> timedelta: ...
     def utcoffset(self, dt: datetime | None) -> timedelta: ...
     def tzname(self, dt: datetime | None) -> str: ...
+    def __deepcopy__(self: Self, memo: dict[int, Any]) -> Self: ...
 
 def timedelta_seconds(td: timedelta) -> int: ...
 def timezone(utcoffset: float) -> str: ...