diff --git a/docs/ref/class-based-views/mixins-editing.txt b/docs/ref/class-based-views/mixins-editing.txt
index a0160610d20..23b781c2e43 100644
--- a/docs/ref/class-based-views/mixins-editing.txt
+++ b/docs/ref/class-based-views/mixins-editing.txt
@@ -37,6 +37,8 @@ FormMixin
 
     .. attribute:: prefix
 
+        .. versionadded:: 1.6
+
         Sets the :attr:`~django.forms.Form.prefix` for the generated form.
 
     .. method:: get_initial()