diff --git a/projects/policyengine-api-simulation/src/modal/gateway/endpoints.py b/projects/policyengine-api-simulation/src/modal/gateway/endpoints.py
index a4716f147..5571b2d29 100644
--- a/projects/policyengine-api-simulation/src/modal/gateway/endpoints.py
+++ b/projects/policyengine-api-simulation/src/modal/gateway/endpoints.py
@@ -100,6 +100,7 @@ def _build_budget_window_parent_payload(
     payload = request.model_dump(
         exclude={"telemetry"},
         mode="json",
+        exclude_none=True,
     )
     payload["version"] = resolved_version
     if request.telemetry is not None:
@@ -162,6 +163,7 @@ async def submit_simulation(request: SimulationRequest):
     payload = request.model_dump(
         exclude={"version", "telemetry"},
         mode="json",
+        exclude_none=True,
     )
     run_id = request.telemetry.run_id if request.telemetry else None
     if request.telemetry is not None:
diff --git a/projects/policyengine-api-simulation/tests/gateway/test_endpoints.py b/projects/policyengine-api-simulation/tests/gateway/test_endpoints.py
index 1dd3715ff..fb4de34ce 100644
--- a/projects/policyengine-api-simulation/tests/gateway/test_endpoints.py
+++ b/projects/policyengine-api-simulation/tests/gateway/test_endpoints.py
@@ -167,6 +167,8 @@ def test__given_no_data_value__then_routes_to_run_simulation(
             "policyengine-simulation-us1-500-0-uk2-66-0",
             "run_simulation",
         )
+        assert "time_period" not in mock_modal["func"].last_payload
+        assert "data_version" not in mock_modal["func"].last_payload
 
     def test__given_submission__then_returns_job_id_and_poll_url(
         self, mock_modal, client: TestClient