diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 2c818d9253..1ae0e5d939 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -2411,7 +2411,7 @@ ROLLBACK;
 -- Secondly test the case of a parallel aggregate combiner function
 -- returning NULL. For that use normal transition function, but a
 -- combiner function returning NULL.
-BEGIN ISOLATION LEVEL REPEATABLE READ;
+BEGIN;
 CREATE FUNCTION balkifnull(int8, int8)
 RETURNS int8
 PARALLEL SAFE
@@ -2453,7 +2453,7 @@ SELECT balk(hundred) FROM tenk1;
 
 ROLLBACK;
 -- test coverage for aggregate combine/serial/deserial functions
-BEGIN ISOLATION LEVEL REPEATABLE READ;
+BEGIN;
 SET parallel_setup_cost = 0;
 SET parallel_tuple_cost = 0;
 SET min_parallel_table_scan_size = 0;
diff --git a/src/test/regress/expected/explain.out b/src/test/regress/expected/explain.out
index dc7ab2ce8b..791eba8511 100644
--- a/src/test/regress/expected/explain.out
+++ b/src/test/regress/expected/explain.out
@@ -293,9 +293,7 @@ rollback;
 -- actually get (maybe none at all), we can't examine the "Workers" output
 -- in any detail.  We can check that it parses correctly as JSON, and then
 -- remove it from the displayed results.
--- 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/insert_parallel.out b/src/test/regress/expected/insert_parallel.out
index d5fae79031..3599c21eba 100644
--- a/src/test/regress/expected/insert_parallel.out
+++ b/src/test/regress/expected/insert_parallel.out
@@ -52,9 +52,7 @@ insert into test_data select * from generate_series(1,10);
 --
 -- END: setup some tables and data needed by the tests.
 --
--- 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/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 9b0c418db7..05ebcb284a 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..77705f9a70 100644
--- a/src/test/regress/expected/write_parallel.out
+++ b/src/test/regress/expected/write_parallel.out
@@ -1,16 +1,14 @@
 --
 -- 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;
 set min_parallel_table_scan_size=0;
 set max_parallel_workers_per_gather=4;
 --
--- Test write operations that has an underlying query that is eligble
+-- Test write operations that has an underlying query that is eligible
 -- for parallel plans
 --
 explain (costs off) create table parallel_write as
diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index f9579af19a..eb53668299 100644
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -1002,7 +1002,7 @@ ROLLBACK;
 -- Secondly test the case of a parallel aggregate combiner function
 -- returning NULL. For that use normal transition function, but a
 -- combiner function returning NULL.
-BEGIN ISOLATION LEVEL REPEATABLE READ;
+BEGIN;
 CREATE FUNCTION balkifnull(int8, int8)
 RETURNS int8
 PARALLEL SAFE
@@ -1035,7 +1035,7 @@ SELECT balk(hundred) FROM tenk1;
 ROLLBACK;
 
 -- test coverage for aggregate combine/serial/deserial functions
-BEGIN ISOLATION LEVEL REPEATABLE READ;
+BEGIN;
 
 SET parallel_setup_cost = 0;
 SET parallel_tuple_cost = 0;
diff --git a/src/test/regress/sql/explain.sql b/src/test/regress/sql/explain.sql
index c79116c927..f2eab030d6 100644
--- a/src/test/regress/sql/explain.sql
+++ b/src/test/regress/sql/explain.sql
@@ -83,9 +83,7 @@ rollback;
 -- in any detail.  We can check that it parses correctly as JSON, and then
 -- remove it from the displayed results.
 
--- 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/insert_parallel.sql b/src/test/regress/sql/insert_parallel.sql
index 70ad31a087..8eb4e9564e 100644
--- a/src/test/regress/sql/insert_parallel.sql
+++ b/src/test/regress/sql/insert_parallel.sql
@@ -66,9 +66,7 @@ insert into test_data select * from generate_series(1,10);
 -- END: setup some tables and data needed by the tests.
 --
 
--- 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/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 5a01a98b26..d31e290ec2 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..a5d63112c9 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;
@@ -13,7 +11,7 @@ set min_parallel_table_scan_size=0;
 set max_parallel_workers_per_gather=4;
 
 --
--- Test write operations that has an underlying query that is eligble
+-- Test write operations that has an underlying query that is eligible
 -- for parallel plans
 --
 explain (costs off) create table parallel_write as