diff --git a/test_runner/regress/test_pg_regress.py b/test_runner/regress/test_pg_regress.py
index a3fae97327..0fea706888 100644
--- a/test_runner/regress/test_pg_regress.py
+++ b/test_runner/regress/test_pg_regress.py
@@ -239,6 +239,8 @@ def test_isolation(
             "neon.regress_test_mode = true",
             # Stack size should be increased for tests to pass with asan.
             "max_stack_depth = 4MB",
+            # Neon extensiosn starts 2 BGW so decreasing number of parallel workers which can affect deadlock-parallel test if it hits max_worker_processes.
+            "max_worker_processes = 16",
         ],
     )
     endpoint.safe_psql(f"CREATE DATABASE {DBNAME}")