diff --git a/requirements-tests.txt b/requirements-tests.txt
index 31c12c50bc2b..aac6873bc6da 100644
--- a/requirements-tests.txt
+++ b/requirements-tests.txt
@@ -1,6 +1,6 @@
 # Type checkers that we test our stubs against. These should always
 # be pinned to a specific version to make failure reproducible.
-mypy==1.18.2
+mypy @ git+https://github.com/python/mypy@6aa44da
 pyright==1.1.406
 
 # Libraries used by our various scripts.
diff --git a/stdlib/builtins.pyi b/stdlib/builtins.pyi
index 969d1687611c..3e72aab90fbe 100644
--- a/stdlib/builtins.pyi
+++ b/stdlib/builtins.pyi
@@ -950,9 +950,20 @@ class memoryview(Sequence[_I]):
     if sys.version_info >= (3, 14):
         def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
+class _Truthy(Protocol):
+    def __bool__(self) -> Literal[True]: ...
+
+class _Falsy(Protocol):
+    def __bool__(self) -> Literal[False]: ...
+
 @final
 class bool(int):
-    def __new__(cls, o: object = False, /) -> Self: ...
+    @overload
+    def __new__(cls, o: _Truthy, /) -> Literal[True]: ...
+    @overload
+    def __new__(cls, o: _Falsy = False, /) -> Literal[False]: ...
+    @overload
+    def __new__(cls, o: object, /) -> Self: ...
     # The following overloads could be represented more elegantly with a TypeVar("_B", bool, int),
     # however mypy has a bug regarding TypeVar constraints (https://github.com/python/mypy/issues/11880).
     @overload