diff --git a/stdlib/2.7/typing.pyi b/stdlib/2.7/typing.pyi
index 0cfeffb60..1a50b7685 100644
--- a/stdlib/2.7/typing.pyi
+++ b/stdlib/2.7/typing.pyi
@@ -187,6 +187,8 @@ class MutableMapping(Mapping[_KT, _VT], Generic[_KT, _VT]):
 
 Text = unicode
 
+TYPE_CHECKING = True
+
 class IO(Iterable[AnyStr], Generic[AnyStr]):
     # TODO detach
     # TODO use abstract properties
diff --git a/stdlib/3/typing.pyi b/stdlib/3/typing.pyi
index f3031e59c..449242458 100644
--- a/stdlib/3/typing.pyi
+++ b/stdlib/3/typing.pyi
@@ -254,6 +254,8 @@ class MutableMapping(Mapping[_KT, _VT], Generic[_KT, _VT]):
 
 Text = str
 
+TYPE_CHECKING = True
+
 class IO(Iterable[AnyStr], Generic[AnyStr]):
     # TODO detach
     # TODO use abstract properties