diff --git a/Modules/_bz2module.c b/Modules/_bz2module.c
index d75bb32d2fc..798e9efc628 100644
--- a/Modules/_bz2module.c
+++ b/Modules/_bz2module.c
@@ -422,7 +422,7 @@ static PyType_Spec bz2_compressor_type_spec = {
     // bz2_compressor_type_spec does not have Py_TPFLAGS_BASETYPE flag
     // which prevents to create a subclass.
     // So calling PyType_GetModuleState() in this file is always safe.
-    .flags = Py_TPFLAGS_DEFAULT,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = bz2_compressor_type_slots,
 };
 
@@ -766,7 +766,7 @@ static PyType_Spec bz2_decompressor_type_spec = {
     // bz2_decompressor_type_spec does not have Py_TPFLAGS_BASETYPE flag
     // which prevents to create a subclass.
     // So calling PyType_GetModuleState() in this file is always safe.
-    .flags = Py_TPFLAGS_DEFAULT,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = bz2_decompressor_type_slots,
 };
 
diff --git a/Modules/_csv.c b/Modules/_csv.c
index a213734f508..78855b87135 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -537,7 +537,8 @@ static PyType_Slot Dialect_Type_slots[] = {
 PyType_Spec Dialect_Type_spec = {
     .name = "_csv.Dialect",
     .basicsize = sizeof(DialectObj),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = Dialect_Type_slots,
 };
 
@@ -958,7 +959,8 @@ static PyType_Slot Reader_Type_slots[] = {
 PyType_Spec Reader_Type_spec = {
     .name = "_csv.reader",
     .basicsize = sizeof(ReaderObj),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = Reader_Type_slots
 };
 
@@ -1382,7 +1384,8 @@ static PyType_Slot Writer_Type_slots[] = {
 PyType_Spec Writer_Type_spec = {
     .name = "_csv.writer",
     .basicsize = sizeof(WriterObj),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = Writer_Type_slots,
 };
 
diff --git a/Modules/_dbmmodule.c b/Modules/_dbmmodule.c
index 2b4d071b3d1..3fe97eff158 100644
--- a/Modules/_dbmmodule.c
+++ b/Modules/_dbmmodule.c
@@ -423,7 +423,7 @@ static PyType_Spec dbmtype_spec = {
     // which prevents to create a subclass.
     // So calling PyType_GetModuleState() in this file is always safe.
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
-              Py_TPFLAGS_HAVE_GC),
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = dbmtype_spec_slots,
 };
 
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index 218a8d16ac3..fa145216809 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -491,7 +491,8 @@ static PyType_Spec partial_type_spec = {
     .name = "functools.partial",
     .basicsize = sizeof(partialobject),
     .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-             Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
+             Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL |
+             Py_TPFLAGS_IMMUTABLETYPE,
     .slots = partial_type_slots
 };
 
@@ -559,7 +560,7 @@ static PyType_Spec keyobject_type_spec = {
     .name = "functools.KeyWrapper",
     .basicsize = sizeof(keyobject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
-              Py_TPFLAGS_HAVE_GC),
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = keyobject_type_slots
 };
 
@@ -781,7 +782,8 @@ static PyType_Slot lru_list_elem_type_slots[] = {
 static PyType_Spec lru_list_elem_type_spec = {
     .name = "functools._lru_list_elem",
     .basicsize = sizeof(lru_list_elem),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
+    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
+             Py_TPFLAGS_IMMUTABLETYPE,
     .slots = lru_list_elem_type_slots
 };
 
@@ -1417,7 +1419,7 @@ static PyType_Spec lru_cache_type_spec = {
     .name = "functools._lru_cache_wrapper",
     .basicsize = sizeof(lru_cache_object),
     .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-             Py_TPFLAGS_METHOD_DESCRIPTOR,
+             Py_TPFLAGS_METHOD_DESCRIPTOR | Py_TPFLAGS_IMMUTABLETYPE,
     .slots = lru_cache_type_slots
 };
 
diff --git a/Modules/_gdbmmodule.c b/Modules/_gdbmmodule.c
index 98bfa6ab996..8a8c6e78259 100644
--- a/Modules/_gdbmmodule.c
+++ b/Modules/_gdbmmodule.c
@@ -581,7 +581,7 @@ static PyType_Spec gdbmtype_spec = {
     // which prevents to create a subclass.
     // So calling PyType_GetModuleState() in this file is always safe.
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
-              Py_TPFLAGS_HAVE_GC),
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = gdbmtype_spec_slots,
 };
 
diff --git a/Modules/_lsprof.c b/Modules/_lsprof.c
index a0e6afa8440..703067cc743 100644
--- a/Modules/_lsprof.c
+++ b/Modules/_lsprof.c
@@ -812,7 +812,8 @@ static PyType_Slot _lsprof_profiler_type_spec_slots[] = {
 static PyType_Spec _lsprof_profiler_type_spec = {
     .name = "_lsprof.Profiler",
     .basicsize = sizeof(ProfilerObject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = _lsprof_profiler_type_spec_slots,
 };
 
diff --git a/Modules/_lzmamodule.c b/Modules/_lzmamodule.c
index 2f80bf0496b..915c0c918f6 100644
--- a/Modules/_lzmamodule.c
+++ b/Modules/_lzmamodule.c
@@ -915,7 +915,7 @@ static PyType_Spec lzma_compressor_type_spec = {
     // lzma_compressor_type_spec does not have Py_TPFLAGS_BASETYPE flag
     // which prevents to create a subclass.
     // So calling PyType_GetModuleState() in this file is always safe.
-    .flags = Py_TPFLAGS_DEFAULT,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = lzma_compressor_type_slots,
 };
 
@@ -1359,7 +1359,7 @@ static PyType_Spec lzma_decompressor_type_spec = {
     // lzma_decompressor_type_spec does not have Py_TPFLAGS_BASETYPE flag
     // which prevents to create a subclass.
     // So calling PyType_GetModuleState() in this file is always safe.
-    .flags = Py_TPFLAGS_DEFAULT,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = lzma_decompressor_type_slots,
 };
 
diff --git a/Modules/_operator.c b/Modules/_operator.c
index 5bd5a3bcb9b..d5e092e2f82 100644
--- a/Modules/_operator.c
+++ b/Modules/_operator.c
@@ -1133,7 +1133,8 @@ static PyType_Spec itemgetter_type_spec = {
     .name = "operator.itemgetter",
     .basicsize = sizeof(itemgetterobject),
     .itemsize = 0,
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = itemgetter_type_slots,
 };
 
@@ -1464,7 +1465,8 @@ static PyType_Spec attrgetter_type_spec = {
     .name = "operator.attrgetter",
     .basicsize = sizeof(attrgetterobject),
     .itemsize = 0,
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = attrgetter_type_slots,
 };
 
@@ -1719,7 +1721,8 @@ static PyType_Spec methodcaller_type_spec = {
     .name = "operator.methodcaller",
     .basicsize = sizeof(methodcallerobject),
     .itemsize = 0,
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = methodcaller_type_slots,
 };
 
diff --git a/Modules/_queuemodule.c b/Modules/_queuemodule.c
index 5e0f38f387a..a124255a72c 100644
--- a/Modules/_queuemodule.c
+++ b/Modules/_queuemodule.c
@@ -380,7 +380,8 @@ static PyType_Slot simplequeue_slots[] = {
 static PyType_Spec simplequeue_spec = {
     .name = "_queue.SimpleQueue",
     .basicsize = sizeof(simplequeueobject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = simplequeue_slots,
 };
 
diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
index 915515c0a19..e1eef587c44 100644
--- a/Modules/_sqlite/connection.c
+++ b/Modules/_sqlite/connection.c
@@ -1914,7 +1914,8 @@ static PyType_Slot connection_slots[] = {
 static PyType_Spec connection_spec = {
     .name = MODULE_NAME ".Connection",
     .basicsize = sizeof(pysqlite_Connection),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = connection_slots,
 };
 
diff --git a/Modules/_sqlite/cursor.c b/Modules/_sqlite/cursor.c
index 8c8a347f46e..8e7d65faa28 100644
--- a/Modules/_sqlite/cursor.c
+++ b/Modules/_sqlite/cursor.c
@@ -1078,7 +1078,8 @@ static PyType_Slot cursor_slots[] = {
 static PyType_Spec cursor_spec = {
     .name = MODULE_NAME ".Cursor",
     .basicsize = sizeof(pysqlite_Cursor),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = cursor_slots,
 };
 
diff --git a/Modules/_sqlite/prepare_protocol.c b/Modules/_sqlite/prepare_protocol.c
index 1f9d7b751d2..cefb46e390a 100644
--- a/Modules/_sqlite/prepare_protocol.c
+++ b/Modules/_sqlite/prepare_protocol.c
@@ -56,7 +56,8 @@ static PyType_Slot type_slots[] = {
 static PyType_Spec type_spec = {
     .name = MODULE_NAME ".PrepareProtocol",
     .basicsize = sizeof(pysqlite_PrepareProtocol),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = type_slots,
 };
 
diff --git a/Modules/_sqlite/row.c b/Modules/_sqlite/row.c
index bf43dad4473..d2f9bdd00b6 100644
--- a/Modules/_sqlite/row.c
+++ b/Modules/_sqlite/row.c
@@ -258,7 +258,8 @@ static PyType_Slot row_slots[] = {
 static PyType_Spec row_spec = {
     .name = MODULE_NAME ".Row",
     .basicsize = sizeof(pysqlite_Row),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = row_slots,
 };
 
diff --git a/Modules/_sqlite/statement.c b/Modules/_sqlite/statement.c
index 89fe4bbec3e..3960b21c859 100644
--- a/Modules/_sqlite/statement.c
+++ b/Modules/_sqlite/statement.c
@@ -502,7 +502,8 @@ static PyType_Slot stmt_slots[] = {
 static PyType_Spec stmt_spec = {
     .name = MODULE_NAME ".Statement",
     .basicsize = sizeof(pysqlite_Statement),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = stmt_slots,
 };
 
diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 3f7f1d23bc9..bee69f2099c 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -313,7 +313,7 @@ static PyType_Spec lock_type_spec = {
     .name = "_thread.lock",
     .basicsize = sizeof(lockobject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-              Py_TPFLAGS_DISALLOW_INSTANTIATION),
+              Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = lock_type_slots,
 };
 
@@ -594,7 +594,8 @@ static PyType_Slot rlock_type_slots[] = {
 static PyType_Spec rlock_type_spec = {
     .name = "_thread.RLock",
     .basicsize = sizeof(rlockobject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = rlock_type_slots,
 };
 
@@ -693,7 +694,8 @@ static PyType_Slot local_dummy_type_slots[] = {
 static PyType_Spec local_dummy_type_spec = {
     .name = "_thread._localdummy",
     .basicsize = sizeof(localdummyobject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = local_dummy_type_slots,
 };
 
@@ -977,7 +979,8 @@ static PyType_Slot local_type_slots[] = {
 static PyType_Spec local_type_spec = {
     .name = "_thread._local",
     .basicsize = sizeof(localobject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = local_type_slots,
 };
 
diff --git a/Modules/_winapi.c b/Modules/_winapi.c
index 2c034628e34..1b85d7dd7ee 100644
--- a/Modules/_winapi.c
+++ b/Modules/_winapi.c
@@ -348,7 +348,7 @@ static PyType_Spec winapi_overlapped_type_spec = {
     .name = "_winapi.Overlapped",
     .basicsize = sizeof(OverlappedObject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
-              Py_TPFLAGS_HAVE_GC),
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = winapi_overlapped_type_slots,
 };
 
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 30fb7c97243..1d9d4cd591a 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -2997,7 +2997,7 @@ static PyType_Spec arrayiter_spec = {
     .name = "array.arrayiterator",
     .basicsize = sizeof(arrayiterobject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-              Py_TPFLAGS_DISALLOW_INSTANTIATION),
+              Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = arrayiter_slots,
 };
 
diff --git a/Modules/cjkcodecs/multibytecodec.c b/Modules/cjkcodecs/multibytecodec.c
index cb7182ff21f..ba558d0dbf2 100644
--- a/Modules/cjkcodecs/multibytecodec.c
+++ b/Modules/cjkcodecs/multibytecodec.c
@@ -749,7 +749,7 @@ static PyType_Spec multibytecodec_spec = {
     .name = MODULE_NAME ".MultibyteCodec",
     .basicsize = sizeof(MultibyteCodecObject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-              Py_TPFLAGS_DISALLOW_INSTANTIATION),
+              Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = multibytecodec_slots,
 };
 
@@ -1111,7 +1111,8 @@ static PyType_Slot encoder_slots[] = {
 static PyType_Spec encoder_spec = {
     .name = MODULE_NAME ".MultibyteIncrementalEncoder",
     .basicsize = sizeof(MultibyteIncrementalEncoderObject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = encoder_slots,
 };
 
@@ -1384,7 +1385,8 @@ static PyType_Slot decoder_slots[] = {
 static PyType_Spec decoder_spec = {
     .name = MODULE_NAME ".MultibyteIncrementalDecoder",
     .basicsize = sizeof(MultibyteIncrementalDecoderObject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = decoder_slots,
 };
 
@@ -1705,7 +1707,8 @@ static PyType_Slot reader_slots[] = {
 static PyType_Spec reader_spec = {
     .name = MODULE_NAME ".MultibyteStreamReader",
     .basicsize = sizeof(MultibyteStreamReaderObject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = reader_slots,
 };
 
@@ -1925,7 +1928,8 @@ static PyType_Slot writer_slots[] = {
 static PyType_Spec writer_spec = {
     .name = MODULE_NAME ".MultibyteStreamWriter",
     .basicsize = sizeof(MultibyteStreamWriterObject),
-    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_IMMUTABLETYPE),
     .slots = writer_slots,
 };
 
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index 8327ba677ec..6397b0d4b81 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -1121,7 +1121,8 @@ static PyType_Slot mmap_object_slots[] = {
 static PyType_Spec mmap_object_spec = {
     .name = "mmap.mmap",
     .basicsize = sizeof(mmap_object),
-    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC),
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = mmap_object_slots,
 };
 
diff --git a/Modules/overlapped.c b/Modules/overlapped.c
index 38dd98f0848..7c4570896bc 100644
--- a/Modules/overlapped.c
+++ b/Modules/overlapped.c
@@ -1876,7 +1876,7 @@ static PyType_Slot overlapped_type_slots[] = {
 static PyType_Spec overlapped_type_spec = {
     .name = "_overlapped.Overlapped",
     .basicsize = sizeof(OverlappedObject),
-    .flags = Py_TPFLAGS_DEFAULT,
+    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = overlapped_type_slots
 };
 
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 9b04df36f52..ec684638ead 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1504,7 +1504,7 @@ static PyType_Spec _xml_parse_type_spec = {
     .name = "pyexpat.xmlparser",
     .basicsize = sizeof(xmlparseobject),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-              Py_TPFLAGS_DISALLOW_INSTANTIATION),
+              Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = _xml_parse_type_spec_slots,
 };
 
diff --git a/Modules/unicodedata.c b/Modules/unicodedata.c
index a4b8193fbc2..26ac68bdca6 100644
--- a/Modules/unicodedata.c
+++ b/Modules/unicodedata.c
@@ -1465,7 +1465,7 @@ static PyType_Spec ucd_type_spec = {
     .name = "unicodedata.UCD",
     .basicsize = sizeof(PreviousDBVersion),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
-              Py_TPFLAGS_HAVE_GC),
+              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
     .slots = ucd_type_slots
 };