diff --git a/thrift/lib/py3/test/auto_migrate/structs.py b/thrift/lib/py3/test/auto_migrate/structs.py
index d5b37d2b323..7df71f5fc77 100644
--- a/thrift/lib/py3/test/auto_migrate/structs.py
+++ b/thrift/lib/py3/test/auto_migrate/structs.py
@@ -489,3 +489,8 @@ def test_included_struct_const(self) -> None:
             FANCY_CONST.color_map,
             {IncludedColour.red: Basic(), IncludedColour.blue: Basic(nom="b")},
         )
+
+    @brokenInAutoMigrate()
+    def test_instance_base_class(self) -> None:
+        self.assertTrue(issubclass(Nested1, Struct))
+        self.assertIsInstance(Nested1(), Struct)
diff --git a/thrift/lib/py3/test/auto_migrate/unions.py b/thrift/lib/py3/test/auto_migrate/unions.py
index 0b7f6bb2a78..7ada13fd0a2 100644
--- a/thrift/lib/py3/test/auto_migrate/unions.py
+++ b/thrift/lib/py3/test/auto_migrate/unions.py
@@ -189,3 +189,8 @@ def test_reserved_union(self) -> None:
         self.assertEqual(x.type, ReservedUnion.Type.ok)
         self.assertEqual(x.value, "bar")
         self.assertEqual(x.ok, "bar")
+
+    @brokenInAutoMigrate()
+    def test_instance_base_class(self) -> None:
+        self.assertTrue(issubclass(ComplexUnion, Union))
+        self.assertIsInstance(ComplexUnion(tiny=1), Union)
diff --git a/thrift/lib/python/test/structs.py b/thrift/lib/python/test/structs.py
index e37acceacb8..df40e01c0d7 100644
--- a/thrift/lib/python/test/structs.py
+++ b/thrift/lib/python/test/structs.py
@@ -71,7 +71,7 @@
     to_thrift_set,
 )
 
-from thrift.python.types import isset, update_nested_field
+from thrift.python.types import isset, Struct, update_nested_field
 
 ListT = TypeVar("ListT")
 SetT = TypeVar("SetT")
@@ -701,3 +701,7 @@ def test_compare_optional(self) -> None:
         with self.assertRaises(TypeError):
             # TODO(ffrancet): pyre should complain about this
             z < y  # noqa: B015
+
+    def test_instance_base_class(self) -> None:
+        self.assertTrue(issubclass(Nested1, Struct))
+        self.assertIsInstance(Nested1(), Struct)
diff --git a/thrift/lib/python/test/unions.py b/thrift/lib/python/test/unions.py
index 06ab37f5a1e..21700b6944e 100644
--- a/thrift/lib/python/test/unions.py
+++ b/thrift/lib/python/test/unions.py
@@ -322,3 +322,7 @@ def test_union_ordering(self) -> None:
         # equality
         y = self.Integers(tiny=4)
         self.assertEqual(x, y)
+
+    def test_instance_base_class(self) -> None:
+        self.assertTrue(issubclass(ComplexUnion, Union))
+        self.assertIsInstance(ComplexUnion(tiny=1), Union)