diff --git a/stdlib/3/configparser.pyi b/stdlib/3/configparser.pyi
index 17501c1e9..3f59b611b 100644
--- a/stdlib/3/configparser.pyi
+++ b/stdlib/3/configparser.pyi
@@ -4,7 +4,7 @@
 import sys
 from typing import (AbstractSet, MutableMapping, Mapping, Dict, Sequence, List,
                     Union, Iterable, Iterator, Callable, Any, IO, overload,
-                    Optional, Pattern, Type, TypeVar)
+                    Optional, Pattern, Type, TypeVar, ClassVar)
 # Types only used in type comments only
 from typing import Optional, Tuple  # noqa
 
@@ -57,6 +57,7 @@ class LegacyInterpolation(Interpolation): ...
 
 
 class RawConfigParser(_parser):
+    BOOLEAN_STATES: ClassVar[Mapping[str, bool]] = ...  # Undocumented
     def __init__(self,
                  defaults: Optional[_section] = ...,
                  dict_type: Type[Mapping[str, str]] = ...,