diff --git a/docs/values.rst b/docs/values.rst
index cf2e7bf..3728148 100644
--- a/docs/values.rst
+++ b/docs/values.rst
@@ -234,6 +234,8 @@ Type values
 
     A :class:`~Value` subclass that handles positive integer values.
 
+    .. versionadded:: 2.1
+
     ::
 
         MYSITE_WORKER_POOL = values.PositiveIntegerValue(8)