diff --git a/Misc/NEWS.d/next/Security/2024-10-29-09-15-10.gh-issue-126108.eTIjHY.rst b/Misc/NEWS.d/next/Security/2024-10-29-09-15-10.gh-issue-126108.eTIjHY.rst
new file mode 100644
index 00000000000000..9f2c7e84d4dff0
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2024-10-29-09-15-10.gh-issue-126108.eTIjHY.rst
@@ -0,0 +1 @@
+Fix a possible ``NULL`` pointer dereference in :c:func:`!PySys_AddWarnOptionUnicode`.
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index d41fe8223deb3f..1f7cc655c45ed0 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -2653,6 +2653,7 @@ PySys_ResetWarnOptions(void)
 static int
 _PySys_AddWarnOptionWithError(PyThreadState *tstate, PyObject *option)
 {
+    assert(tstate != NULL);
     PyObject *warnoptions = get_warnoptions(tstate);
     if (warnoptions == NULL) {
         return -1;
@@ -2667,11 +2668,11 @@ void
 PySys_AddWarnOptionUnicode(PyObject *option)
 {
     PyThreadState *tstate = _PyThreadState_GET();
+    _Py_EnsureTstateNotNULL(tstate);
+    assert(!_PyErr_Occurred(tstate));
     if (_PySys_AddWarnOptionWithError(tstate, option) < 0) {
         /* No return value, therefore clear error state if possible */
-        if (tstate) {
-            _PyErr_Clear(tstate);
-        }
+        _PyErr_Clear(tstate);
     }
 }