diff --git a/src/test/regress/expected/union.out b/src/test/regress/expected/union.out
index 6a7d0f2a88..a678e960d4 100644
--- a/src/test/regress/expected/union.out
+++ b/src/test/regress/expected/union.out
@@ -551,6 +551,28 @@ explain (costs off)
 reset enable_seqscan;
 reset enable_indexscan;
 reset enable_bitmapscan;
+-- This simpler variant of the above test has been observed to fail differently
+create table events (event_id int primary key);
+create table other_events (event_id int primary key);
+create table events_child () inherits (events);
+explain (costs off)
+select event_id
+ from (select event_id from events
+       union all
+       select event_id from other_events) ss
+ order by event_id;
+                        QUERY PLAN                        
+----------------------------------------------------------
+ Merge Append
+   Sort Key: events.event_id
+   ->  Index Scan using events_pkey on events
+   ->  Sort
+         Sort Key: events_child.event_id
+         ->  Seq Scan on events_child
+   ->  Index Scan using other_events_pkey on other_events
+(7 rows)
+
+drop table events_child, events, other_events;
 reset enable_indexonlyscan;
 -- Test constraint exclusion of UNION ALL subqueries
 explain (costs off)
diff --git a/src/test/regress/sql/union.sql b/src/test/regress/sql/union.sql
index 5205435e2f..9ff1551e5d 100644
--- a/src/test/regress/sql/union.sql
+++ b/src/test/regress/sql/union.sql
@@ -229,6 +229,22 @@ explain (costs off)
 reset enable_seqscan;
 reset enable_indexscan;
 reset enable_bitmapscan;
+
+-- This simpler variant of the above test has been observed to fail differently
+
+create table events (event_id int primary key);
+create table other_events (event_id int primary key);
+create table events_child () inherits (events);
+
+explain (costs off)
+select event_id
+ from (select event_id from events
+       union all
+       select event_id from other_events) ss
+ order by event_id;
+
+drop table events_child, events, other_events;
+
 reset enable_indexonlyscan;
 
 -- Test constraint exclusion of UNION ALL subqueries