diff --git a/src/blueapi/worker/task.py b/src/blueapi/worker/task.py
index 91ecbfcda..02ad15a20 100644
--- a/src/blueapi/worker/task.py
+++ b/src/blueapi/worker/task.py
@@ -22,7 +22,8 @@ class Task(BlueapiBaseModel):
 
     def prepare_params(self, ctx: BlueskyContext) -> Mapping[str, Any]:
         model = _lookup_params(ctx, self)
-        return _model_to_kwargs(model)
+        # Re-create dict manually to avoid nesting in model_dump output
+        return {field: getattr(model, field) for field in model.__pydantic_fields__}
 
     def do_task(self, ctx: BlueskyContext) -> None:
         LOGGER.info(f"Asked to run plan {self.name} with {self.params}")
@@ -49,22 +50,3 @@ def _lookup_params(ctx: BlueskyContext, task: Task) -> BaseModel:
     model = plan.model
     adapter = TypeAdapter(model)
     return adapter.validate_python(task.params)
-
-
-def _model_to_kwargs(model: BaseModel) -> Mapping[str, Any]:
-    """
-    Converts an instance of BaseModel back to a dictionary that
-    can be passed as **kwargs.
-    Used instead of BaseModel.model_dump() because we don't want
-    the dumping to be nested and because it fires UserWarnings
-    about data types it is unfamiliar with
-    (such as ophyd devices).
-
-    Args:
-        model: Pydantic model to convert to kwargs
-
-    Returns:
-        Mapping[str, Any]: Dictionary that can be passed as **kwargs
-    """
-
-    return {name: getattr(model, name) for name in model.model_fields_set}
diff --git a/tests/unit_tests/worker/test_task_worker.py b/tests/unit_tests/worker/test_task_worker.py
index 1eae7280c..d593821dc 100644
--- a/tests/unit_tests/worker/test_task_worker.py
+++ b/tests/unit_tests/worker/test_task_worker.py
@@ -575,3 +575,26 @@ def test_begin_task_span_ok(
     task_id = worker.submit_task(_SIMPLE_TASK)
     with asserting_span_exporter(exporter, "begin_task", "task_id"):
         worker.begin_task(task_id)
+
+
+def test_injected_devices_are_found(
+    fake_device: FakeDevice,
+    context: BlueskyContext,
+):
+    def injected_device_plan(dev: FakeDevice = fake_device.name) -> MsgGenerator:  # type: ignore
+        yield from ()
+
+    context.register_plan(injected_device_plan)
+    params = Task(name="injected_device_plan").prepare_params(context)
+    assert params["dev"] == fake_device
+
+
+def test_missing_injected_devices_fail_early(
+    context: BlueskyContext,
+):
+    def missing_injection(dev: FakeDevice = "does_not_exist") -> MsgGenerator:  # type: ignore
+        yield from ()
+
+    context.register_plan(missing_injection)
+    with pytest.raises(ValueError):
+        Task(name="missing_injection").prepare_params(context)