diff --git a/reference/forms/types/options/translation_domain.rst.inc b/reference/forms/types/options/translation_domain.rst.inc
index 5317f2c372e..26a40a19dd8 100644
--- a/reference/forms/types/options/translation_domain.rst.inc
+++ b/reference/forms/types/options/translation_domain.rst.inc
@@ -1,7 +1,9 @@
 translation_domain
 ~~~~~~~~~~~~~~~~~~
 
-**type**: ``string`` **default**: ``messages``
+**type**: ``string``, ``null`` or ``false``  **default**: ``null``
 
 This is the translation domain that will be used for any labels or options
-that are rendered for this field.
+that are rendered for this field. Use null to use the translation domain of
+the parent form or the default domain of translator for root form. Use false
+to disable translation.