diff --git a/contrib/amcheck/expected/check_btree.out b/contrib/amcheck/expected/check_btree.out
index f82f48d23b..13848b7449 100644
--- a/contrib/amcheck/expected/check_btree.out
+++ b/contrib/amcheck/expected/check_btree.out
@@ -155,11 +155,19 @@ SELECT bt_index_parent_check('delete_test_table_pkey', true);
 -- tuple.  Bloom filter must fingerprint normalized index tuple representation.
 --
 CREATE TABLE toast_bug(buggy text);
-ALTER TABLE toast_bug ALTER COLUMN buggy SET STORAGE plain;
--- pg_attribute entry for toasty.buggy will have plain storage:
-CREATE INDEX toasty ON toast_bug(buggy);
--- Whereas pg_attribute entry for toast_bug.buggy now has extended storage:
 ALTER TABLE toast_bug ALTER COLUMN buggy SET STORAGE extended;
+CREATE INDEX toasty ON toast_bug(buggy);
+-- pg_attribute entry for toasty.buggy (the index) will have plain storage:
+UPDATE pg_attribute SET attstorage = 'p'
+WHERE attrelid = 'toasty'::regclass AND attname = 'buggy';
+-- Whereas pg_attribute entry for toast_bug.buggy (the table) still has extended storage:
+SELECT attstorage FROM pg_attribute
+WHERE attrelid = 'toast_bug'::regclass AND attname = 'buggy';
+ attstorage 
+------------
+ x
+(1 row)
+
 -- Insert compressible heap tuple (comfortably exceeds TOAST_TUPLE_THRESHOLD):
 INSERT INTO toast_bug SELECT repeat('a', 2200);
 -- Should not get false positive report of corruption:
diff --git a/contrib/amcheck/sql/check_btree.sql b/contrib/amcheck/sql/check_btree.sql
index a1fef644cb..97a3e1a20d 100644
--- a/contrib/amcheck/sql/check_btree.sql
+++ b/contrib/amcheck/sql/check_btree.sql
@@ -99,11 +99,17 @@ SELECT bt_index_parent_check('delete_test_table_pkey', true);
 -- tuple.  Bloom filter must fingerprint normalized index tuple representation.
 --
 CREATE TABLE toast_bug(buggy text);
-ALTER TABLE toast_bug ALTER COLUMN buggy SET STORAGE plain;
--- pg_attribute entry for toasty.buggy will have plain storage:
-CREATE INDEX toasty ON toast_bug(buggy);
--- Whereas pg_attribute entry for toast_bug.buggy now has extended storage:
 ALTER TABLE toast_bug ALTER COLUMN buggy SET STORAGE extended;
+CREATE INDEX toasty ON toast_bug(buggy);
+
+-- pg_attribute entry for toasty.buggy (the index) will have plain storage:
+UPDATE pg_attribute SET attstorage = 'p'
+WHERE attrelid = 'toasty'::regclass AND attname = 'buggy';
+
+-- Whereas pg_attribute entry for toast_bug.buggy (the table) still has extended storage:
+SELECT attstorage FROM pg_attribute
+WHERE attrelid = 'toast_bug'::regclass AND attname = 'buggy';
+
 -- Insert compressible heap tuple (comfortably exceeds TOAST_TUPLE_THRESHOLD):
 INSERT INTO toast_bug SELECT repeat('a', 2200);
 -- Should not get false positive report of corruption: