diff --git a/src/blueapi/client/client.py b/src/blueapi/client/client.py
index 68637594fa..034b9f6a98 100644
--- a/src/blueapi/client/client.py
+++ b/src/blueapi/client/client.py
@@ -120,23 +120,23 @@ def __repr__(self) -> str:
         return f"DeviceCache({len(self._cache)} devices)"
 
 
-class DeviceRef(str):
+class DeviceRef:
+    name: str
     model: DeviceModel
     _cache: DeviceCache
 
-    def __new__(cls, name: str, cache: DeviceCache, model: DeviceModel):
-        instance = super().__new__(cls, name)
-        instance.model = model
-        instance._cache = cache
-        return instance
+    def __init__(self, name: str, cache: DeviceCache, model: DeviceModel):
+        self.name = name
+        self.model = model
+        self._cache = cache
 
     def __getattr__(self, name) -> "DeviceRef":
         if name.startswith("_"):
             raise AttributeError(f"No child device named {name}")
-        return self._cache[f"{self}.{name}"]
+        return self._cache[f"{self.name}.{name}"]
 
     def __repr__(self):
-        return f"Device({self})"
+        return f"Device({self.name})"
 
 
 class Plan:
diff --git a/src/blueapi/client/rest.py b/src/blueapi/client/rest.py
index cacbc1656c..0bddb5c87c 100644
--- a/src/blueapi/client/rest.py
+++ b/src/blueapi/client/rest.py
@@ -11,8 +11,10 @@
     start_as_current_span,
 )
 from pydantic import BaseModel, TypeAdapter, ValidationError
+from pydantic_core import PydanticSerializationError
 
 from blueapi import __version__
+from blueapi.client import client
 from blueapi.config import RestConfig
 from blueapi.service.authentication import JWTAuth, SessionManager
 from blueapi.service.model import (
@@ -241,7 +243,7 @@ def create_task(self, task: TaskRequest) -> TaskResponse:
             TaskResponse,
             method="POST",
             get_exception=_create_task_exceptions,
-            data=task.model_dump(),
+            data=task.model_dump(mode="json", fallback=_task_model_fallback),
         )
 
     def clear_task(self, task_id: str) -> TaskResponse:
@@ -363,3 +365,10 @@ def __getattr__(name: str):
 
 class ServiceUnavailableError(Exception):
     pass
+
+
+def _task_model_fallback(obj: Any) -> Any:
+    """Fallback method for serializing TaskRequests"""
+    if isinstance(obj, client.DeviceRef):
+        return obj.name
+    raise PydanticSerializationError(f"Object of type {type(obj)} not serializable")
diff --git a/tests/unit_tests/client/test_client.py b/tests/unit_tests/client/test_client.py
index 169d727f62..125fc165c2 100644
--- a/tests/unit_tests/client/test_client.py
+++ b/tests/unit_tests/client/test_client.py
@@ -202,9 +202,9 @@ def test_get_child_device(mock_rest: Mock, client: BlueapiClient):
         else None
     )
     foo = client.devices.foo
-    assert foo == "foo"
+    assert foo.name == "foo"
     x = client.devices.foo.x
-    assert x == "foo.x"
+    assert x.name == "foo.x"
 
 
 def test_state_property(client: BlueapiClient):
diff --git a/tests/unit_tests/client/test_rest.py b/tests/unit_tests/client/test_rest.py
index 0de1c94277..c3386ad552 100644
--- a/tests/unit_tests/client/test_rest.py
+++ b/tests/unit_tests/client/test_rest.py
@@ -8,9 +8,11 @@
 import requests
 import responses
 from packaging.version import Version
+from pydantic_core import PydanticSerializationError
 from responses import DELETE, GET, PUT, matchers
 
 from blueapi import __version__
+from blueapi.client.client import DeviceRef
 from blueapi.client.rest import (
     BlueapiRestClient,
     BlueskyRemoteControlError,
@@ -29,6 +31,7 @@
     DeviceModel,
     EnvironmentResponse,
     PlanModel,
+    TaskRequest,
     TaskResponse,
     TasksListResponse,
     WorkerTask,
@@ -77,6 +80,45 @@ def test_rest_error_code(
         rest.get_plans()
 
 
+def test_create_task_serialization():
+    rest = Mock(spec=BlueapiRestClient)
+    request = TaskRequest(
+        name="demo",
+        instrument_session="cm12345-1",
+        params={"devices": [DeviceRef(name="foo", cache=Mock(), model=Mock())]},
+    )
+
+    BlueapiRestClient.create_task(rest, request)
+
+    rest._request_and_deserialize.assert_called_once_with(
+        "/tasks",
+        TaskResponse,
+        method="POST",
+        get_exception=_create_task_exceptions,
+        data={
+            "name": "demo",
+            "instrument_session": "cm12345-1",
+            "params": {"devices": ["foo"]},
+        },
+    )
+
+
+def test_create_task_serialization_error():
+    class CustomType:
+        pass
+
+    rest = Mock(spec=BlueapiRestClient)
+    request = TaskRequest(
+        name="demo",
+        instrument_session="cm12345-1",
+        params={"devices": [CustomType()]},
+    )
+
+    with pytest.raises(PydanticSerializationError, match="not serializable"):
+        BlueapiRestClient.create_task(rest, request)
+    rest._request_and_deserialize.assert_not_called()
+
+
 @pytest.mark.parametrize(
     "code,content,expected_exception",
     [