diff --git a/tests/sqllogic/connection.py b/tests/sqllogic/connection.py
index 66e03b25cb48..24b0ff0d0ddd 100644
--- a/tests/sqllogic/connection.py
+++ b/tests/sqllogic/connection.py
@@ -103,6 +103,7 @@ def default_clickhouse_native_conn_args():
             "max_bytes_before_external_sort": 128 * 1024 * 1024,
             "max_bytes_ratio_before_external_group_by": 0.0,
             "max_bytes_ratio_before_external_sort": 0.0,
+            "max_threads": 1,
         }
     )
 
diff --git a/tests/sqllogic/runner.py b/tests/sqllogic/runner.py
index 5b7b4dd9f2e2..bd4c9818f53f 100755
--- a/tests/sqllogic/runner.py
+++ b/tests/sqllogic/runner.py
@@ -142,7 +142,9 @@ def _child_process(setup_kwargs, runner_kwargs, input_dir, output_dir, test):
 
 
 def run_all_tests_in_parallel(setup_kwargs, runner_kwargs, input_dir, output_dir):
-    process_count = max(1, os.cpu_count() - 4)
+    cpu_count = os.cpu_count() or 2
+    process_count = max(1, min(10, cpu_count - 4))
+    logger.info("Running tests with %s worker processes (cpu_count=%s)", process_count, cpu_count)
     tests = list(TestRunner.list_tests(input_dir))
     with multiprocessing.Pool(process_count) as pool:
         async_results = [