diff --git a/Doc/c-api/tuple.rst b/Doc/c-api/tuple.rst
index 25df397..62bc9a5 100644
--- a/Doc/c-api/tuple.rst
+++ b/Doc/c-api/tuple.rst
@@ -182,10 +182,13 @@
    +-----------+------------------+-----------------------------------------+
 
 
-.. c:var:: char* PyStructSequence_UnnamedField
+.. c:var:: const char * const PyStructSequence_UnnamedField
 
    Special value for a field name to leave it unnamed.
 
+   .. versionchanged:: 3.9
+      The type was changed from ``char *``.
+
 
 .. c:function:: PyObject* PyStructSequence_New(PyTypeObject *type)
 
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index b1beb0b..6e9ddc5 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -215,6 +215,9 @@
   way to call a callable Python object without any argument.
   (Contributed by Victor Stinner in :issue:`37194`.)
 
+* The global variable :c:data:`PyStructSequence_UnnamedField` is now a constant
+  and refers to a constant string.
+  (Contributed by Serhiy Storchaka in :issue:`38650`.)
 
 
 Deprecated