diff --git a/src/test/regress/expected/cte_inline.out b/src/test/regress/expected/cte_inline.out
index 46156ac93..a534a7ac9 100644
--- a/src/test/regress/expected/cte_inline.out
+++ b/src/test/regress/expected/cte_inline.out
@@ -449,6 +449,29 @@ DEBUG:  Creating router plan
 (5 rows)
 
 \set VERBOSITY default
+-- enable_group_by_reordering is a new GUC introduced in PG15
+-- it does some optimization of the order of group by keys which results
+-- in a different explain output plan between PG13/14 and PG15
+-- Hence we set that GUC to off.
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+SET enable_group_by_reordering TO off;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM SET enable_group_by_reordering TO off;$$);
+ ?column?
+---------------------------------------------------------------------
+        1
+(1 row)
+
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+ run_command_on_workers
+---------------------------------------------------------------------
+ (localhost,57637,t,t)
+ (localhost,57638,t,t)
+(2 rows)
+
 EXPLAIN (COSTS OFF) WITH cte_1 AS NOT MATERIALIZED (SELECT * FROM test_table)
 SELECT
 	count(*)
@@ -487,6 +510,22 @@ DEBUG:  join prunable for intervals [1073741824,2147483647] and [0,1073741823]
                                  ->  Seq Scan on test_table_1960000 test_table_1
 (12 rows)
 
+\if :server_version_above_fourteen
+RESET enable_group_by_reordering;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM RESET enable_group_by_reordering;$$);
+ ?column?
+---------------------------------------------------------------------
+        1
+(1 row)
+
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+ run_command_on_workers
+---------------------------------------------------------------------
+ (localhost,57637,t,t)
+ (localhost,57638,t,t)
+(2 rows)
+
 -- ctes with volatile functions are not
 -- inlined
 WITH cte_1 AS (SELECT *, random() FROM test_table)
diff --git a/src/test/regress/expected/multi_explain.out b/src/test/regress/expected/multi_explain.out
index 8d4d00d36..86435fe86 100644
--- a/src/test/regress/expected/multi_explain.out
+++ b/src/test/regress/expected/multi_explain.out
@@ -632,6 +632,21 @@ Aggregate
                                             ->  Seq Scan on events_1400285 events
                                                   Filter: ((event_type)::text = ANY ('{click,submit,pay}'::text[]))
 -- Union and left join subquery pushdown
+-- enable_group_by_reordering is a new GUC introduced in PG15
+-- it does some optimization of the order of group by keys which results
+-- in a different explain output plan between PG13/14 and PG15
+-- Hence we set that GUC to off.
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+SET enable_group_by_reordering TO off;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM SET enable_group_by_reordering TO off;$$);
+1
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+(localhost,57637,t,t)
+(localhost,57638,t,t)
 EXPLAIN (COSTS OFF)
 SELECT
 	avg(array_length(events, 1)) AS event_average,
@@ -854,6 +869,14 @@ Sort
                                                                                 Sort Key: events_2.composite_id
                                                                                 ->  Seq Scan on events_1400285 events_2
                                                                                       Filter: ((composite_id >= '(1,-9223372036854775808)'::user_composite_type) AND (composite_id <= '(1,9223372036854775807)'::user_composite_type) AND ((event_type)::text = 'pay'::text))
+\if :server_version_above_fourteen
+RESET enable_group_by_reordering;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM RESET enable_group_by_reordering;$$);
+1
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+(localhost,57637,t,t)
+(localhost,57638,t,t)
 -- Lateral join subquery pushdown
 -- set subquery_pushdown due to limit in the query
 SET citus.subquery_pushdown to ON;
diff --git a/src/test/regress/sql/cte_inline.sql b/src/test/regress/sql/cte_inline.sql
index 8c70bc13f..c554d5df9 100644
--- a/src/test/regress/sql/cte_inline.sql
+++ b/src/test/regress/sql/cte_inline.sql
@@ -236,6 +236,19 @@ $Q$);
 
 \set VERBOSITY default
 
+-- enable_group_by_reordering is a new GUC introduced in PG15
+-- it does some optimization of the order of group by keys which results
+-- in a different explain output plan between PG13/14 and PG15
+-- Hence we set that GUC to off.
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+SET enable_group_by_reordering TO off;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM SET enable_group_by_reordering TO off;$$);
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+
 EXPLAIN (COSTS OFF) WITH cte_1 AS NOT MATERIALIZED (SELECT * FROM test_table)
 SELECT
 	count(*)
@@ -245,6 +258,11 @@ FROM
 	cte_1 as second_entry
 		USING (key);
 
+\if :server_version_above_fourteen
+RESET enable_group_by_reordering;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM RESET enable_group_by_reordering;$$);
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
 
 
 -- ctes with volatile functions are not
diff --git a/src/test/regress/sql/multi_explain.sql b/src/test/regress/sql/multi_explain.sql
index 505eda13e..3b2cf26d6 100644
--- a/src/test/regress/sql/multi_explain.sql
+++ b/src/test/regress/sql/multi_explain.sql
@@ -250,6 +250,20 @@ FROM
 		user_id) AS subquery;
 
 -- Union and left join subquery pushdown
+
+-- enable_group_by_reordering is a new GUC introduced in PG15
+-- it does some optimization of the order of group by keys which results
+-- in a different explain output plan between PG13/14 and PG15
+-- Hence we set that GUC to off.
+SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int > 14 AS server_version_above_fourteen
+\gset
+\if :server_version_above_fourteen
+SET enable_group_by_reordering TO off;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM SET enable_group_by_reordering TO off;$$);
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+
 EXPLAIN (COSTS OFF)
 SELECT
 	avg(array_length(events, 1)) AS event_average,
@@ -385,6 +399,12 @@ GROUP BY
 ORDER BY
 	count_pay;
 
+\if :server_version_above_fourteen
+RESET enable_group_by_reordering;
+\endif
+SELECT DISTINCT 1 FROM run_command_on_workers($$ALTER SYSTEM RESET enable_group_by_reordering;$$);
+SELECT run_command_on_workers($$SELECT pg_reload_conf()$$);
+
 -- Lateral join subquery pushdown
 -- set subquery_pushdown due to limit in the query
 SET citus.subquery_pushdown to ON;