diff --git a/sphinx/util/typing.py b/sphinx/util/typing.py
index 4450d4edb..bd2a2ad38 100644
--- a/sphinx/util/typing.py
+++ b/sphinx/util/typing.py
@@ -121,7 +121,10 @@ def restify(cls: Optional[Type]) -> str:
             else:
                 return ' | '.join(restify(a) for a in cls.__args__)
         elif cls.__module__ in ('__builtin__', 'builtins'):
-            return ':class:`%s`' % cls.__name__
+            if hasattr(cls, '__args__'):
+                return ':class:`%s`\\[%s]' % (cls.__name__, ', '.join(restify(arg) for arg in cls.__args__))
+            else:
+                return ':class:`%s`' % cls.__name__
         else:
             if sys.version_info >= (3, 7):  # py37+
                 return _restify_py37(cls)