From 3274eeea5775e6efd49e8ca2c06ea5e4c140c40e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Sun, 12 Oct 2025 11:00:14 +0200
Subject: [PATCH] fix a leak when failing to create a Union type

---
 .../2025-10-12-11-00-06.gh-issue-139988.4wi51t.rst              | 2 ++
 Objects/unionobject.c                                           | 2 ++
 2 files changed, 4 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-10-12-11-00-06.gh-issue-139988.4wi51t.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-10-12-11-00-06.gh-issue-139988.4wi51t.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-12-11-00-06.gh-issue-139988.4wi51t.rst
new file mode 100644
index 00000000000000..60fa3b1d339cb1
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-12-11-00-06.gh-issue-139988.4wi51t.rst
@@ -0,0 +1,2 @@
+Fix a memory leak when failing to create a :class:`~typing.Union` type.
+Patch by Bénédikt Tran.
diff --git a/Objects/unionobject.c b/Objects/unionobject.c
index 2206ed80ef03fd..c4ece0fe09f018 100644
--- a/Objects/unionobject.c
+++ b/Objects/unionobject.c
@@ -474,11 +474,13 @@ _Py_union_from_tuple(PyObject *args)
     }
     if (PyTuple_CheckExact(args)) {
         if (!unionbuilder_add_tuple(&ub, args)) {
+            unionbuilder_finalize(&ub);
             return NULL;
         }
     }
     else {
         if (!unionbuilder_add_single(&ub, args)) {
+            unionbuilder_finalize(&ub);
             return NULL;
         }
     }