diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 0eca76cb41..2712853e67 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -3,9 +3,7 @@
 --
 create function sp_parallel_restricted(int) returns int as
   $$begin return $1; end$$ language plpgsql parallel restricted;
--- Serializable isolation would disable parallel query, so explicitly use an
--- arbitrary other level.
-begin isolation level repeatable read;
+begin;
 -- encourage use of parallel plans
 set parallel_setup_cost=0;
 set parallel_tuple_cost=0;
diff --git a/src/test/regress/expected/write_parallel.out b/src/test/regress/expected/write_parallel.out
index 0c4da2591a..0d12bf4812 100644
--- a/src/test/regress/expected/write_parallel.out
+++ b/src/test/regress/expected/write_parallel.out
@@ -1,9 +1,7 @@
 --
 -- PARALLEL
 --
--- Serializable isolation would disable parallel query, so explicitly use an
--- arbitrary other level.
-begin isolation level repeatable read;
+begin;
 -- encourage use of parallel plans
 set parallel_setup_cost=0;
 set parallel_tuple_cost=0;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 03c056b8b7..0677775194 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -5,9 +5,7 @@
 create function sp_parallel_restricted(int) returns int as
   $$begin return $1; end$$ language plpgsql parallel restricted;
 
--- Serializable isolation would disable parallel query, so explicitly use an
--- arbitrary other level.
-begin isolation level repeatable read;
+begin;
 
 -- encourage use of parallel plans
 set parallel_setup_cost=0;
diff --git a/src/test/regress/sql/write_parallel.sql b/src/test/regress/sql/write_parallel.sql
index 78b479cedf..3259d3696b 100644
--- a/src/test/regress/sql/write_parallel.sql
+++ b/src/test/regress/sql/write_parallel.sql
@@ -2,9 +2,7 @@
 -- PARALLEL
 --
 
--- Serializable isolation would disable parallel query, so explicitly use an
--- arbitrary other level.
-begin isolation level repeatable read;
+begin;
 
 -- encourage use of parallel plans
 set parallel_setup_cost=0;