diff --git a/mypy/main.py b/mypy/main.py
index 1d4fca7858683..49067ce91fea5 100644
--- a/mypy/main.py
+++ b/mypy/main.py
@@ -85,7 +85,7 @@ def type_check_only(sources: List[BuildSource],
 MYPYPATH     additional module search path"""
 
 
-class SplitNamespace:
+class SplitNamespace(argparse.Namespace):
     def __init__(self, standard_namespace: object, alt_namespace: object, alt_prefix: str) -> None:
         self.__dict__['_standard_namespace'] = standard_namespace
         self.__dict__['_alt_namespace'] = alt_namespace
diff --git a/test-data/stdlib-samples/3.2/test/test_random.py b/test-data/stdlib-samples/3.2/test/test_random.py
index cec22efc0b832..5989ceeee2bbb 100644
--- a/test-data/stdlib-samples/3.2/test/test_random.py
+++ b/test-data/stdlib-samples/3.2/test/test_random.py
@@ -46,7 +46,7 @@ def test_seedargs(self) -> None:
         for arg in [list(range(3)), {'one': 1}]:
             self.assertRaises(TypeError, self.gen.seed, arg)
         self.assertRaises(TypeError, self.gen.seed, 1, 2, 3, 4)
-        self.assertRaises(TypeError, type(self.gen), [])
+        self.assertRaises(TypeError, type(self.gen), [])  # type: ignore  # mypy issue 1846
 
     def test_choice(self) -> None:
         choice = self.gen.choice
diff --git a/typeshed b/typeshed
index 8515cf5de86d5..b63e09c239052 160000
--- a/typeshed
+++ b/typeshed
@@ -1 +1 @@
-Subproject commit 8515cf5de86d5e1de9c996b1ec62ab580fddc201
+Subproject commit b63e09c2390523be8252d37abf25fee26eff9656