diff --git a/python/google/protobuf/internal/message_test.py b/python/google/protobuf/internal/message_test.py
index 80ec6e4f69..94347aaf1d 100755
--- a/python/google/protobuf/internal/message_test.py
+++ b/python/google/protobuf/internal/message_test.py
@@ -1406,6 +1406,12 @@ class Proto2Test(unittest.TestCase):
     with self.assertRaises(ValueError):
       m.unknown_map_field[1] = 123
 
+  def testDeepCopyClosedEnum(self):
+    m = map_proto2_unittest_pb2.TestEnumMap()
+    m.known_map_field[123] = 0
+    m2 = copy.deepcopy(m)
+    self.assertEqual(m, m2)
+
   def testExtensionsErrors(self):
     msg = unittest_pb2.TestAllTypes()
     self.assertRaises(AttributeError, getattr, msg, 'Extensions')
diff --git a/upb/message/copy.c b/upb/message/copy.c
index 5d77ab8c61..2643456d08 100644
--- a/upb/message/copy.c
+++ b/upb/message/copy.c
@@ -98,7 +98,7 @@ upb_Map* upb_Map_DeepClone(const upb_Map* map, upb_CType key_type,
     const upb_MiniTableField* value_field =
         &map_entry_table->UPB_PRIVATE(fields)[1];
     const upb_MiniTable* value_sub =
-        (value_field->UPB_PRIVATE(submsg_index) != kUpb_NoSub)
+        upb_MiniTableField_CType(value_field) == kUpb_CType_Message
             ? upb_MiniTable_GetSubMessageTable(map_entry_table, value_field)
             : NULL;
     upb_CType value_field_type = upb_MiniTableField_CType(value_field);
@@ -165,8 +165,7 @@ static bool upb_Message_Array_DeepClone(const upb_Array* array,
   UPB_PRIVATE(_upb_MiniTableField_CheckIsArray)(field);
   upb_Array* cloned_array = upb_Array_DeepClone(
       array, upb_MiniTableField_CType(field),
-      upb_MiniTableField_CType(field) == kUpb_CType_Message &&
-              field->UPB_PRIVATE(submsg_index) != kUpb_NoSub
+      upb_MiniTableField_CType(field) == kUpb_CType_Message
           ? upb_MiniTable_GetSubMessageTable(mini_table, field)
           : NULL,
       arena);