python · vstinner · Mar 6, 2026 · Mar 5, 2026
diff --git a/Doc/library/marshal.rst b/Doc/library/marshal.rst
@@ -51,8 +51,9 @@ this module.  The following types are supported:
 * Strings (:class:`str`) and :class:`bytes`.
  :term:`Bytes-like objects <bytes-like object>` like :class:`bytearray` are
  marshalled as :class:`!bytes`.
-* Containers: :class:`tuple`, :class:`list`, :class:`set`, :class:`frozenset`,
-  and (since :data:`version` 5), :class:`slice`.
+* Containers: :class:`tuple`, :class:`list`, :class:`dict`, :class:`frozendict`
+  (since :data:`version` 6), :class:`set`, :class:`frozenset`, and
+  :class:`slice` (since :data:`version` 5).
  It should be understood that these are supported only if the values contained
  therein are themselves supported.
  Recursive containers are supported since :data:`version` 3.
@@ -71,6 +72,10 @@ this module.  The following types are supported:

   Added format version 5, which allows marshalling slices.

+.. versionchanged:: next
+
+   Added format version 6, which allows marshalling :class:`frozendict`.
+

 The module defines these functions:

@@ -173,6 +178,8 @@ In addition, the following constants are defined:
   4       Python 3.4      Efficient representation of short strings
   ------- --------------- ----------------------------------------------------
   5       Python 3.14     Support for :class:`slice` objects
+   ------- --------------- ----------------------------------------------------
+   6       Python 3.15     Support for :class:`frozendict` objects
   ======= =============== ====================================================



diff --git a/Include/cpython/marshal.h b/Include/cpython/marshal.h
@@ -6,7 +6,7 @@ PyAPI_FUNC(PyObject *) PyMarshal_ReadObjectFromString(const char *,
                                                      Py_ssize_t);
 PyAPI_FUNC(PyObject *) PyMarshal_WriteObjectToString(PyObject *, int);

-#define Py_MARSHAL_VERSION 5
+#define Py_MARSHAL_VERSION 6

 PyAPI_FUNC(long) PyMarshal_ReadLongFromFile(FILE *);
 PyAPI_FUNC(int) PyMarshal_ReadShortFromFile(FILE *);

diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
@@ -570,6 +570,15 @@ def testDict(self):
            self.helper(dictobj)
            self.helper3(dictobj)

+    def testFrozenDict(self):
+        for obj in self.keys:
+            dictobj = frozendict({"hello": obj, "goodbye": obj, obj: "hello"})
+            self.helper(dictobj)
+
+            for version in range(6):
+                with self.assertRaises(ValueError):
+                    marshal.dumps(dictobj, version)
+
    def testModule(self):
        with open(__file__, "rb") as f:
            code = f.read()
@@ -635,7 +644,7 @@ def test_slice(self):
            with self.subTest(obj=str(obj)):
                self.helper(obj)

-                for version in range(4):
+                for version in range(5):
                    with self.assertRaises(ValueError):
                        marshal.dumps(obj, version)


diff --git a/Misc/NEWS.d/next/Library/2026-03-05-16-06-09.gh-issue-141510.dFPAQS.rst b/Misc/NEWS.d/next/Library/2026-03-05-16-06-09.gh-issue-141510.dFPAQS.rst
@@ -0,0 +1,2 @@
+:mod:`marshal` now supports :class:`frozendict` objects. The marshal format
+version was increased to 6. Patch by Victor Stinner.
@@ -134,7 +134,7 @@ compile_and_marshal(const char *name, const char *text)
        return NULL;
    }

-    assert(Py_MARSHAL_VERSION >= 5);
+    assert(Py_MARSHAL_VERSION >= 6);
    PyObject *marshalled = PyMarshal_WriteObjectToString(code, Py_MARSHAL_VERSION);
    Py_CLEAR(code);
    if (marshalled == NULL) {

diff --git a/Python/marshal.c b/Python/marshal.c
@@ -580,6 +580,12 @@ w_complex_object(PyObject *v, char flag, WFILE *p)
        Py_ssize_t pos;
        PyObject *key, *value;
        if (PyFrozenDict_CheckExact(v)) {
+            if (p->version < 6) {
+                w_byte(TYPE_UNKNOWN, p);
+                p->error = WFERR_UNMARSHALLABLE;
+                return;
+            }
+
            W_TYPE(TYPE_FROZENDICT, p);
        }
        else {
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		:mod:`marshal` now supports :class:`frozendict` objects. The marshal format
		version was increased to 6. Patch by Victor Stinner.