diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index 0b1df7e68b8dfa..49ddfd5b43b00c 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -121,7 +121,7 @@ PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
 
 extern void _Py_AddRefTotal(PyThreadState *, Py_ssize_t);
 extern PyAPI_FUNC(void) _Py_IncRefTotal(PyThreadState *);
-extern void _Py_DecRefTotal(PyThreadState *);
+extern PyAPI_FUNC(void) _Py_DecRefTotal(PyThreadState *);
 
 #  define _Py_DEC_REFTOTAL(interp) \
     interp->object_state.reftotal--
@@ -710,7 +710,7 @@ _PyObject_SetMaybeWeakref(PyObject *op)
     }
 }
 
-extern int _PyObject_ResurrectEndSlow(PyObject *op);
+extern PyAPI_FUNC(int) _PyObject_ResurrectEndSlow(PyObject *op);
 #endif
 
 // Temporarily resurrects an object during deallocation. The refcount is set
diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py
index 7a052817766a07..e53cbf0036e265 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -2710,6 +2710,19 @@ def __str__(self):
 
             self.assertEqual(sys.getrefcount(obj), initial_refcount)
 
+    def test_subclass_fail_to_propagate_del(self):
+        # gh-129289: Fix subclass of asyncio.Task not propagating __del__() causes segfault.
+        class BadTask(self.Task):
+            def __del__(self):
+                pass
+
+        async def func():
+            return
+
+        task = BadTask(func(), loop=self.loop)
+
+        result = self.loop.run_until_complete(task)
+
 
 def add_subclass_tests(cls):
     BaseTask = cls.Task
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-02-07-12-58-23.gh-issue-129289.tHkEC-.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-07-12-58-23.gh-issue-129289.tHkEC-.rst
new file mode 100644
index 00000000000000..c790acfae91917
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-07-12-58-23.gh-issue-129289.tHkEC-.rst
@@ -0,0 +1 @@
+Fix subclass of :class:`asyncio.Task` not propagating finalizer causes segfault.
diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
index 656c03a98d73b2..68d8294dbeaada 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -3075,6 +3075,16 @@ TaskObj_dealloc(PyObject *self)
         // resurrected.
         return;
     }
+    if (task->task_node.next != NULL) {
+        if (PyErr_WarnEx(PyExc_Warning, "subclasses of asyncio.Task must propagate __del__()", 1) < 0) {
+            PyErr_Clear();
+        }
+        _PyObject_ResurrectStart(self);
+        TaskObj_finalize(task);
+        if (_PyObject_ResurrectEnd(self)) {
+            return;
+        }
+    }
 
     PyTypeObject *tp = Py_TYPE(task);
     PyObject_GC_UnTrack(self);