diff --git a/testing/typing_checks.py b/testing/typing_checks.py
index d15b3988b..80b8c9f82 100644
--- a/testing/typing_checks.py
+++ b/testing/typing_checks.py
@@ -4,11 +4,13 @@ This file is not executed, it is only checked by mypy to ensure that
 none of the code triggers any mypy errors.
 """
 import contextlib
+import sys
 from typing import Optional
 
 from typing_extensions import assert_type
 
 import pytest
+from _pytest.monkeypatch import MonkeyPatch
 
 
 # Issue #7488.
@@ -29,6 +31,16 @@ def check_parametrize_ids_callable(func) -> None:
     pass
 
 
+# Issue #10999.
+@pytest.mark.skipif(sys.version_info < (3, 8), reason="TypedDict introduced in Python 3.8")
+def check_monkeypatch_typeddict(monkeypatch: MonkeyPatch) -> None:
+    from typing import TypedDict
+
+    Foo = TypedDict("Foo", {"x": int, "y": float})
+    a: Foo = {"x": 1, "y": 3.14}
+    monkeypatch.setitem("x", 2)
+    monkeypatch.delitem("y")
+
 def check_raises_is_a_context_manager(val: bool) -> None:
     with pytest.raises(RuntimeError) if val else contextlib.nullcontext() as excinfo:
         pass