diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c
index f4b7dcac21..5aac6d6677 100644
--- a/src/backend/optimizer/path/pathkeys.c
+++ b/src/backend/optimizer/path/pathkeys.c
@@ -397,6 +397,11 @@ group_keys_reorder_by_pathkeys(List *pathkeys, List **group_pathkeys,
 			!list_member_ptr(*group_pathkeys, pathkey))
 			break;
 
+		/*
+		 * Since 1349d27 pathkey coming from underlying node can be in the
+		 * root->group_pathkeys but not in the processed_groupClause. So, we
+		 * should be careful here.
+		 */
 		sgc = get_sortgroupref_clause_noerr(pathkey->pk_eclass->ec_sortref,
 											*group_clauses);
 		if (!sgc)
diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 423c8ec3b6..0d46e096e5 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -2857,6 +2857,28 @@ explain (COSTS OFF) SELECT x,w FROM btg GROUP BY w,x,y,z ORDER BY x*x,z;
 (8 rows)
 
 DROP TABLE btg;
+-- The case, when scanning sort order correspond to aggregate sort order but
+-- can not be found in the group-by list
+CREATE TABLE t1 (c1 int PRIMARY KEY, c2 int);
+CREATE UNIQUE INDEX ON t1(c2);
+explain (costs off)
+SELECT array_agg(c1 ORDER BY c2),c2
+FROM t1 WHERE c2 < 100 GROUP BY c1 ORDER BY 2;
+                       QUERY PLAN                       
+--------------------------------------------------------
+ Sort
+   Sort Key: c2
+   ->  GroupAggregate
+         Group Key: c1
+         ->  Sort
+               Sort Key: c1, c2
+               ->  Bitmap Heap Scan on t1
+                     Recheck Cond: (c2 < 100)
+                     ->  Bitmap Index Scan on t1_c2_idx
+                           Index Cond: (c2 < 100)
+(10 rows)
+
+DROP TABLE t1 CASCADE;
 RESET enable_hashagg;
 RESET max_parallel_workers;
 RESET max_parallel_workers_per_gather;
diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index b9fcceedd7..f99167ac9e 100644
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -1224,6 +1224,15 @@ explain (COSTS OFF) SELECT x,w FROM btg GROUP BY w,x,y,z ORDER BY x*x,z;
 
 DROP TABLE btg;
 
+-- The case, when scanning sort order correspond to aggregate sort order but
+-- can not be found in the group-by list
+CREATE TABLE t1 (c1 int PRIMARY KEY, c2 int);
+CREATE UNIQUE INDEX ON t1(c2);
+explain (costs off)
+SELECT array_agg(c1 ORDER BY c2),c2
+FROM t1 WHERE c2 < 100 GROUP BY c1 ORDER BY 2;
+DROP TABLE t1 CASCADE;
+
 RESET enable_hashagg;
 RESET max_parallel_workers;
 RESET max_parallel_workers_per_gather;