diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ebc62034d2..85dcc33063 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -5761,6 +5761,14 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
 				foreach(lc, dropped_attrs)
 					newslot->tts_isnull[lfirst_int(lc)] = true;
 
+				/*
+				 * Constraints and GENERATED expressions might reference the
+				 * tableoid column, so fill tts_tableOid with the desired
+				 * value.  (We must do this each time, because it gets
+				 * overwritten with newrel's OID during storing.)
+				 */
+				newslot->tts_tableOid = RelationGetRelid(oldrel);
+
 				/*
 				 * Process supplied expressions to replace selected columns.
 				 *
@@ -5804,11 +5812,6 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
 									   &newslot->tts_isnull[ex->attnum - 1]);
 				}
 
-				/*
-				 * Constraints might reference the tableoid column, so
-				 * initialize t_tableOid before evaluating them.
-				 */
-				newslot->tts_tableOid = RelationGetRelid(oldrel);
 				insertslot = newslot;
 			}
 			else
diff --git a/src/test/regress/expected/generated.out b/src/test/regress/expected/generated.out
index 675773f0c1..71542e95d5 100644
--- a/src/test/regress/expected/generated.out
+++ b/src/test/regress/expected/generated.out
@@ -64,6 +64,7 @@ ERROR:  both identity and generation expression specified for column "b" of tabl
 LINE 1: ...t PRIMARY KEY, b int GENERATED ALWAYS AS identity GENERATED ...
                                                              ^
 -- reference to system column not allowed in generated column
+-- (except tableoid, which we test below)
 CREATE TABLE gtest_err_6a (a int PRIMARY KEY, b bool GENERATED ALWAYS AS (xmin <> 37) STORED);
 ERROR:  cannot use system column "xmin" in column generation expression
 LINE 1: ...a (a int PRIMARY KEY, b bool GENERATED ALWAYS AS (xmin <> 37...
@@ -455,14 +456,16 @@ DROP TYPE double_int;
 -- using tableoid is allowed
 CREATE TABLE gtest_tableoid (
   a int PRIMARY KEY,
-  b bool GENERATED ALWAYS AS (tableoid <> 0) STORED
+  b bool GENERATED ALWAYS AS (tableoid = 'gtest_tableoid'::regclass) STORED
 );
 INSERT INTO gtest_tableoid VALUES (1), (2);
+ALTER TABLE gtest_tableoid ADD COLUMN
+  c regclass GENERATED ALWAYS AS (tableoid) STORED;
 SELECT * FROM gtest_tableoid;
- a | b 
----+---
- 1 | t
- 2 | t
+ a | b |       c        
+---+---+----------------
+ 1 | t | gtest_tableoid
+ 2 | t | gtest_tableoid
 (2 rows)
 
 -- drop column behavior
diff --git a/src/test/regress/sql/generated.sql b/src/test/regress/sql/generated.sql
index 63251c443a..914197608b 100644
--- a/src/test/regress/sql/generated.sql
+++ b/src/test/regress/sql/generated.sql
@@ -29,6 +29,7 @@ CREATE TABLE gtest_err_5a (a int PRIMARY KEY, b int DEFAULT 5 GENERATED ALWAYS A
 CREATE TABLE gtest_err_5b (a int PRIMARY KEY, b int GENERATED ALWAYS AS identity GENERATED ALWAYS AS (a * 2) STORED);
 
 -- reference to system column not allowed in generated column
+-- (except tableoid, which we test below)
 CREATE TABLE gtest_err_6a (a int PRIMARY KEY, b bool GENERATED ALWAYS AS (xmin <> 37) STORED);
 
 -- various prohibited constructs
@@ -218,9 +219,11 @@ DROP TYPE double_int;
 -- using tableoid is allowed
 CREATE TABLE gtest_tableoid (
   a int PRIMARY KEY,
-  b bool GENERATED ALWAYS AS (tableoid <> 0) STORED
+  b bool GENERATED ALWAYS AS (tableoid = 'gtest_tableoid'::regclass) STORED
 );
 INSERT INTO gtest_tableoid VALUES (1), (2);
+ALTER TABLE gtest_tableoid ADD COLUMN
+  c regclass GENERATED ALWAYS AS (tableoid) STORED;
 SELECT * FROM gtest_tableoid;
 
 -- drop column behavior