diff --git a/doc/src/sgml/ref/alter_domain.sgml b/doc/src/sgml/ref/alter_domain.sgml
index db7b8198350..d65d517bb5f 100644
--- a/doc/src/sgml/ref/alter_domain.sgml
+++ b/doc/src/sgml/ref/alter_domain.sgml
@@ -272,7 +272,8 @@ ALTER DOMAIN name
Currently, ALTER DOMAIN ADD CONSTRAINT> and
- ALTER DOMAIN SET NOT NULL> will fail if the named domain or
+ ALTER DOMAIN SET NOT NULL> will fail if the validated named
+ domain or
any derived domain is used within a composite-type column of any
table in the database. They should eventually be improved to be
able to verify the new constraint for such nested columns.