diff --git a/tests/test_function/cases/__init__.py b/tests/test_function/cases/__init__.py
index 2568f629..bfc5437d 100644
--- a/tests/test_function/cases/__init__.py
+++ b/tests/test_function/cases/__init__.py
@@ -30,6 +30,7 @@
     on_failure,
     parallel_step_disappears,
     parallel_steps,
+    pydantic_event,
     pydantic_output,
     retry_after_error,
     sleep_until,
@@ -73,6 +74,7 @@
     on_failure,
     parallel_step_disappears,
     parallel_steps,
+    pydantic_event,
     pydantic_output,
     retry_after_error,
     sleep_until,
diff --git a/tests/test_function/cases/pydantic_event.py b/tests/test_function/cases/pydantic_event.py
new file mode 100644
index 00000000..a28a389e
--- /dev/null
+++ b/tests/test_function/cases/pydantic_event.py
@@ -0,0 +1,108 @@
+"""
+We don't support returning Pydantic models in steps or functions. This may
+change in the future.
+"""
+
+import json
+import typing
+
+import pydantic
+from typing_extensions import assert_type
+
+import inngest
+import tests.helper
+from inngest._internal import server_lib
+
+from . import base
+
+TEvent = typing.TypeVar("TEvent", bound="BaseEvent")
+
+
+class BaseEvent(pydantic.BaseModel):
+    data: pydantic.BaseModel
+    id: str = ""
+    name: typing.ClassVar[str]
+    ts: int = 0
+
+    @classmethod
+    def from_event(cls: type[TEvent], event: inngest.Event) -> TEvent:
+        return cls.model_validate(event.model_dump(mode="json"))
+
+    def to_event(self) -> inngest.Event:
+        return inngest.Event(
+            name=self.name,
+            data=self.data.model_dump(mode="json"),
+            id=self.id,
+            ts=self.ts,
+        )
+
+
+class MyEventData(pydantic.BaseModel):
+    count: int
+
+
+def create(
+    client: inngest.Inngest,
+    framework: server_lib.Framework,
+    is_sync: bool,
+) -> base.Case:
+    test_name = base.create_test_name(__file__)
+
+    class MyEvent(BaseEvent):
+        data: MyEventData
+        name = base.create_event_name(framework, test_name)
+
+    fn_id = base.create_fn_id(test_name)
+    state = base.BaseState()
+
+    @client.create_function(
+        fn_id=fn_id,
+        retries=0,
+        trigger=inngest.TriggerEvent(event=MyEvent.name),
+    )
+    def fn_sync(
+        ctx: inngest.Context,
+        step: inngest.StepSync,
+    ) -> typing.Any:
+        state.run_id = ctx.run_id
+        event = MyEvent.from_event(ctx.event)
+        assert_type(event, MyEvent)
+        return event.model_dump(mode="json")
+
+    @client.create_function(
+        fn_id=fn_id,
+        retries=0,
+        trigger=inngest.TriggerEvent(event=MyEvent.name),
+    )
+    async def fn_async(
+        ctx: inngest.Context,
+        step: inngest.Step,
+    ) -> typing.Any:
+        state.run_id = ctx.run_id
+        event = MyEvent.from_event(ctx.event)
+        assert_type(event, MyEvent)
+        return event.model_dump(mode="json")
+
+    async def run_test(self: base.TestClass) -> None:
+        self.client.send_sync(MyEvent(data=MyEventData(count=1)).to_event())
+        run = tests.helper.client.wait_for_run_status(
+            state.wait_for_run_id(),
+            tests.helper.RunStatus.COMPLETED,
+        )
+
+        assert run.output is not None
+        event = MyEvent.model_validate(json.loads(run.output))
+        assert event.data.count == 1
+        assert event.id != ""
+        assert event.ts > 0
+
+    if is_sync:
+        fn = fn_sync
+    else:
+        fn = fn_async
+
+    return base.Case(
+        fn=fn,
+        run_test=run_test,
+        name=test_name,
+    )