Value of field "type" must be one of (4,) in a Modal using discord.py 2.0

I am trying to show the user a Modal after they display a button, which contains a dropdown select menu from which they can choose multiple options. This code has functioned in the past, but is not causing an exception. Specifically:

[2022-09-02 22:30:47] [ERROR   ] discord.ui.view: Ignoring exception in view <TestButtonView timeout=180.0 children=1> for item <Button style=<ButtonStyle.primary: 1> url=None disabled=False label='Test' emoji=None row=None>
Traceback (most recent call last):
  File "C:UsersadriaPycharmProjectssblBotvenvlibsite-packagesdiscorduiview.py", line 425, in _scheduled_task
    await item.callback(interaction)
  File "C:UsersadriaPycharmProjectssblBotmain.py", line 1131, in test_button_callback
    await interaction.response.send_modal(TestModal())
  File "C:UsersadriaPycharmProjectssblBotvenvlibsite-packagesdiscordinteractions.py", line 852, in send_modal
    await adapter.create_interaction_response(
  File "C:UsersadriaPycharmProjectssblBotvenvlibsite-packagesdiscordwebhookasync_.py", line 220, in request
    raise HTTPException(response, data)
discord.errors.HTTPException: 400 Bad Request (error code: 50035): Invalid Form Body
In data.components.0.components.0: Value of field "type" must be one of (4,).

I have reduced my code to the minimal reproducible example of my issue. Here is the code for the Modal:

class TestModal(discord.ui.Modal, title='Test'):

    def __init__(self, **kw):
        super().__init__(**kw)

    select = discord.ui.Select(
        placeholder='Select a tier.',
        options=[discord.SelectOption(label='test')]
    )

    async def on_submit(self, interaction: discord.Interaction):
        await interaction.response.defer()

And here is the code for the view with the button (the f):

class TestButtonView(discord.ui.View):
    def __init__(self, **kw):
        super().__init__(**kw)
        self.add_buttons()

    def add_buttons(self):
        test_button = discord.ui.Button(label='Test', style=discord.ButtonStyle.blurple)

        async def test_button_callback(interaction: discord.Interaction):
            await interaction.response.send_modal(TestModal())

        test_button.callback = test_button_callback

        self.add_item(test_button)

And finally, the command to send the button view:

@client.command(hidden=True)
async def test(ctx):
    await ctx.send(view=TestButtonView())