diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index c07083bd448..16f979c8d93 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -116,10 +116,12 @@ test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid c
 # ----------
 # Another group of parallel tests
 # ----------
-test: identity partition_join partition_prune reloptions hash_part indexing partition_aggregate fast_default
+test: identity partition_join partition_prune reloptions hash_part indexing partition_aggregate
 
 # event triggers cannot run concurrently with any test that runs DDL
 test: event_trigger
+# this test also uses event triggers, so likewise run it by itself
+test: fast_default
 
 # run stats by itself because its delay may be insufficient under heavy load
 test: stats
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index e6e6a4608b2..42632be6750 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -188,6 +188,6 @@ test: reloptions
 test: hash_part
 test: indexing
 test: partition_aggregate
-test: fast_default
 test: event_trigger
+test: fast_default
 test: stats