Issue #19795: Mark up None as literal text.
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 246e2e3..9619e53 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -771,7 +771,7 @@
    dictionary containing the class's namespace; :attr:`~class.__bases__` is a
    tuple (possibly empty or a singleton) containing the base classes, in the
    order of their occurrence in the base class list; :attr:`__doc__` is the
-   class's documentation string, or None if undefined;
+   class's documentation string, or ``None`` if undefined;
    :attr:`__annotations__` (optional) is a dictionary containing
    :term:`variable annotations <variable annotation>` collected during
    class body execution.