diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index d25b39bb54..4ebac27d10 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -185,6 +185,8 @@ relationHasPrimaryKey(Relation rel)
  * created NOT NULL during CREATE TABLE), do an ALTER SET NOT NULL to mark
  * them so --- or fail if they are not in fact nonnull.
  *
+ * For ALTER TABLE, SET NOT NULL is applied as well to child tables.
+ *
  * Caller had better have at least ShareLock on the table, else the not-null
  * checking isn't trustworthy.
  */
@@ -253,17 +255,13 @@ index_check_primary_key(Relation heapRel,
 	}
 
 	/*
-	 * XXX: Shouldn't the ALTER TABLE .. SET NOT NULL cascade to child tables?
-	 * Currently, since the PRIMARY KEY itself doesn't cascade, we don't
-	 * cascade the notnull constraint(s) either; but this is pretty debatable.
-	 *
 	 * XXX: possible future improvement: when being called from ALTER TABLE,
 	 * it would be more efficient to merge this with the outer ALTER TABLE, so
 	 * as to avoid two scans.  But that seems to complicate DefineIndex's API
 	 * unduly.
 	 */
 	if (cmds)
-		AlterTableInternal(RelationGetRelid(heapRel), cmds, false);
+		AlterTableInternal(RelationGetRelid(heapRel), cmds, is_alter_table);
 }
 
 /*
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 13d6a4b747..e9fd1aacce 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -328,7 +328,7 @@ Number of child tables: 1 (Use \d+ to list them.)
       Table "public.constraint_rename_test2"
  Column |  Type   | Collation | Nullable | Default 
 --------+---------+-----------+----------+---------
- a      | integer |           |          | 
+ a      | integer |           | not null | 
  b      | integer |           |          | 
  c      | integer |           |          | 
  d      | integer |           |          |