diff --git a/CHANGES.rst b/CHANGES.rst
index 4dd9d5df..8eca4dfb 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,10 @@
+v6.0.1
+======
+
+* #434: Expand protocol for ``PackageMetadata.get_all`` to match
+  the upstream implementation of ``email.message.Message.get_all``
+  in python/typeshed#9620.
+
 v6.0.0
 ======
 
diff --git a/docs/conf.py b/docs/conf.py
index ebfdb74d..8e7762d0 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -61,9 +61,11 @@
     ),
 )
 
-# Workaround for #316
 nitpick_ignore = [
+    # Workaround for #316
     ('py:class', 'importlib_metadata.EntryPoints'),
     ('py:class', 'importlib_metadata.SelectableGroups'),
     ('py:class', 'importlib_metadata._meta._T'),
+    # Workaround for #435
+    ('py:class', '_T'),
 ]
diff --git a/importlib_metadata/_meta.py b/importlib_metadata/_meta.py
index 259b15ba..8621c680 100644
--- a/importlib_metadata/_meta.py
+++ b/importlib_metadata/_meta.py
@@ -1,5 +1,5 @@
 from ._compat import Protocol
-from typing import Any, Dict, Iterator, List, TypeVar, Union
+from typing import Any, Dict, Iterator, List, Optional, TypeVar, Union, overload
 
 
 _T = TypeVar("_T")
@@ -18,7 +18,13 @@ def __getitem__(self, key: str) -> str:
     def __iter__(self) -> Iterator[str]:
         ...  # pragma: no cover
 
-    def get_all(self, name: str, failobj: _T = ...) -> Union[List[Any], _T]:
+    # overload per python/importlib_metadata#435
+    @overload
+    def get_all(self, name: str, failobj: None = None) -> Optional[List[Any]]:
+        ...  # pragma: no cover
+
+    @overload
+    def get_all(self, name: str, failobj: _T) -> Union[List[Any], _T]:
         """
         Return all values associated with a possibly multi-valued key.
         """