diff --git a/contrib/test_decoding/expected/repack.out b/contrib/test_decoding/expected/repack.out
index 1f99f26c1f8..cf93c1f0d3d 100644
--- a/contrib/test_decoding/expected/repack.out
+++ b/contrib/test_decoding/expected/repack.out
@@ -29,3 +29,25 @@ SELECT a.relname, a.relfilenode=b.relfilenode FROM pg_class a
 
 DROP TABLE ptnowner;
 DROP ROLE regress_ptnowner;
+-- Verify that REPACK (CONCURRENTLY) doesn't lose "attmissingval" columns
+CREATE TABLE rpk_missing (id int PRIMARY KEY);
+INSERT INTO rpk_missing SELECT generate_series(1, 3);
+ALTER TABLE rpk_missing ADD COLUMN a int DEFAULT 42;
+SELECT * FROM rpk_missing;
+ id | a  
+----+----
+  1 | 42
+  2 | 42
+  3 | 42
+(3 rows)
+
+REPACK (CONCURRENTLY) rpk_missing;
+SELECT * FROM rpk_missing;
+ id | a  
+----+----
+  1 | 42
+  2 | 42
+  3 | 42
+(3 rows)
+
+DROP TABLE rpk_missing;
diff --git a/contrib/test_decoding/sql/repack.sql b/contrib/test_decoding/sql/repack.sql
index c3bfae61f7f..6164dd4235f 100644
--- a/contrib/test_decoding/sql/repack.sql
+++ b/contrib/test_decoding/sql/repack.sql
@@ -23,3 +23,12 @@ SELECT a.relname, a.relfilenode=b.relfilenode FROM pg_class a
   JOIN ptnowner_oldnodes b USING (oid) ORDER BY a.relname COLLATE "C";
 DROP TABLE ptnowner;
 DROP ROLE regress_ptnowner;
+
+-- Verify that REPACK (CONCURRENTLY) doesn't lose "attmissingval" columns
+CREATE TABLE rpk_missing (id int PRIMARY KEY);
+INSERT INTO rpk_missing SELECT generate_series(1, 3);
+ALTER TABLE rpk_missing ADD COLUMN a int DEFAULT 42;
+SELECT * FROM rpk_missing;
+REPACK (CONCURRENTLY) rpk_missing;
+SELECT * FROM rpk_missing;
+DROP TABLE rpk_missing;
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index 20d3b46e062..2268cc277bc 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2396,10 +2396,10 @@ heap_insert_for_repack(HeapTuple tuple, Relation OldHeap, Relation NewHeap,
 /*
  * Subroutine for reform_and_rewrite_tuple and heap_insert_for_repack.
  *
- * Deform the given tuple, set values of dropped columns to NULL, form a new
- * tuple and return it.  If no attributes need to be changed in this way, a
- * copy of the original tuple is returned.  Caller is responsible for freeing
- * the returned tuple.
+ * Deform the given tuple, set values of dropped columns to NULL, and fill in
+ * any values from attmissingval; then form a new tuple and return it.  If no
+ * attributes need to be changed, a copy of the original tuple is returned.
+ * Caller is responsible for freeing the returned tuple.
  *
  * XXX this coding assumes that both relations have the same tupledesc.
  */
@@ -2411,13 +2411,33 @@ reform_tuple(HeapTuple tuple, Relation OldHeap, Relation NewHeap,
 	TupleDesc	newTupDesc = RelationGetDescr(NewHeap);
 	bool		needs_reform = false;
 
-	/* Skip work if the tuple doesn't need any attributes changed */
-	for (int i = 0; i < newTupDesc->natts; i++)
+	/*
+	 * A short tuple might require values from attmissing val, so activate the
+	 * coding unconditionally in that case.  The value might legitimally be
+	 * NULL otherwise, so this is slightly wasteful, but it probably beats
+	 * having to test each attribute for presence of attmissingval each time.
+	 */
+	if (HeapTupleHeaderGetNatts(tuple->t_data) < newTupDesc->natts)
+		needs_reform = true;
+
+	/*
+	 * If the column has been dropped but a value is still present, we can
+	 * optimize storage now by getting rid of it.
+	 */
+	if (!needs_reform)
 	{
-		if (TupleDescCompactAttr(newTupDesc, i)->attisdropped &&
-			!heap_attisnull(tuple, i + 1, newTupDesc))
-			needs_reform = true;
+		for (int i = 0; i < newTupDesc->natts; i++)
+		{
+			if (TupleDescCompactAttr(newTupDesc, i)->attisdropped &&
+				!heap_attisnull(tuple, i + 1, newTupDesc))
+			{
+				needs_reform = true;
+				break;
+			}
+		}
 	}
+
+	/* Skip work if no changes are needed */
 	if (!needs_reform)
 		return heap_copytuple(tuple);
 
diff --git a/src/test/regress/expected/fast_default.out b/src/test/regress/expected/fast_default.out
index bd142ed481c..5813f1c61a5 100644
--- a/src/test/regress/expected/fast_default.out
+++ b/src/test/regress/expected/fast_default.out
@@ -969,6 +969,42 @@ SELECT count(*)
      0
 (1 row)
 
+-- Verify that table-rewriting maintenance commands preserve attmissingval
+-- columns.
+CREATE TABLE t (id int PRIMARY KEY);
+INSERT INTO t SELECT generate_series(1, 3);
+ALTER TABLE t ADD COLUMN a int DEFAULT 42;
+ALTER TABLE t ADD COLUMN b int NOT NULL DEFAULT 7 CHECK (b > 0);
+VACUUM FULL t;
+SELECT * FROM t ORDER BY id;
+ id | a  | b 
+----+----+---
+  1 | 42 | 7
+  2 | 42 | 7
+  3 | 42 | 7
+(3 rows)
+
+ALTER TABLE t ADD COLUMN c text DEFAULT 'hello';
+CLUSTER t USING t_pkey;
+SELECT * FROM t ORDER BY id;
+ id | a  | b |   c   
+----+----+---+-------
+  1 | 42 | 7 | hello
+  2 | 42 | 7 | hello
+  3 | 42 | 7 | hello
+(3 rows)
+
+ALTER TABLE t ADD COLUMN d int DEFAULT 99;
+REPACK t;
+SELECT * FROM t ORDER BY id;
+ id | a  | b |   c   | d  
+----+----+---+-------+----
+  1 | 42 | 7 | hello | 99
+  2 | 42 | 7 | hello | 99
+  3 | 42 | 7 | hello | 99
+(3 rows)
+
+DROP TABLE t;
 -- cleanup
 DROP FOREIGN TABLE ft1;
 DROP SERVER s0;
diff --git a/src/test/regress/sql/fast_default.sql b/src/test/regress/sql/fast_default.sql
index 8b31d317d73..e5d9a3d2fd1 100644
--- a/src/test/regress/sql/fast_default.sql
+++ b/src/test/regress/sql/fast_default.sql
@@ -653,6 +653,22 @@ SELECT count(*)
   WHERE attrelid = 'ft1'::regclass AND
     (attmissingval IS NOT NULL OR atthasmissing);
 
+-- Verify that table-rewriting maintenance commands preserve attmissingval
+-- columns.
+CREATE TABLE t (id int PRIMARY KEY);
+INSERT INTO t SELECT generate_series(1, 3);
+ALTER TABLE t ADD COLUMN a int DEFAULT 42;
+ALTER TABLE t ADD COLUMN b int NOT NULL DEFAULT 7 CHECK (b > 0);
+VACUUM FULL t;
+SELECT * FROM t ORDER BY id;
+ALTER TABLE t ADD COLUMN c text DEFAULT 'hello';
+CLUSTER t USING t_pkey;
+SELECT * FROM t ORDER BY id;
+ALTER TABLE t ADD COLUMN d int DEFAULT 99;
+REPACK t;
+SELECT * FROM t ORDER BY id;
+DROP TABLE t;
+
 -- cleanup
 DROP FOREIGN TABLE ft1;
 DROP SERVER s0;