diff --git a/scripts/ci/in_container/entrypoint_ci.sh b/scripts/ci/in_container/entrypoint_ci.sh
index 8803e0578cb82..df8afeb587905 100755
--- a/scripts/ci/in_container/entrypoint_ci.sh
+++ b/scripts/ci/in_container/entrypoint_ci.sh
@@ -190,6 +190,15 @@ fi
 # shellcheck source=scripts/ci/in_container/configure_environment.sh
 . "${MY_DIR}/configure_environment.sh"
 
+if [[ ${CI:=} == "true" && ${RUN_TESTS} == "true" ]] ; then
+    echo
+    echo " !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+    echo "  Setting default parallellism to 4 because we can run out of memory during tests on CI"
+    echo " !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+    echo
+    export AIRFLOW__CORE__PARALELLISM=4
+fi
+
 set +u
 # If we do not want to run tests, we simply drop into bash
 if [[ "${RUN_TESTS}" == "false" ]]; then
diff --git a/tests/jobs/test_backfill_job.py b/tests/jobs/test_backfill_job.py
index bf5d9d55409fd..65c481c4259e7 100644
--- a/tests/jobs/test_backfill_job.py
+++ b/tests/jobs/test_backfill_job.py
@@ -160,7 +160,7 @@ def test_backfill_multi_dates(self):
 
         end_date = DEFAULT_DATE + datetime.timedelta(days=1)
 
-        executor = MockExecutor()
+        executor = MockExecutor(parallelism=16)
         job = BackfillJob(
             dag=dag,
             start_date=DEFAULT_DATE,
@@ -710,7 +710,7 @@ def test_backfill_ordered_concurrent_execute(self):
 
         dag.clear()
 
-        executor = MockExecutor()
+        executor = MockExecutor(parallelism=16)
         job = BackfillJob(dag=dag,
                           executor=executor,
                           start_date=DEFAULT_DATE,
@@ -1443,7 +1443,10 @@ def test_backfill_run_backwards(self):
         dag = self.dagbag.get_dag("test_start_date_scheduling")
         dag.clear()
 
+        executor = MockExecutor(parallelism=16)
+
         job = BackfillJob(
+            executor=executor,
             dag=dag,
             start_date=DEFAULT_DATE,
             end_date=DEFAULT_DATE + datetime.timedelta(days=1),