Trying to restrict items to a specific user in a Django Class Based View query set

I have the following models:

class AccountManager(models.Model):
    account_manager = models.ForeignKey(
      settings.AUTH_USER_MODEL, 
      on_delete=models.CASCADE
    )

    def __str__(self):
        return str(self.account_manager)

class Client(models.Model):
    account_manager = models.ForeignKey(AccountManager, on_delete=models.CASCADE, related_name='account_manager_clients')
    client = models.CharField(max_length=255)

    def __str__(self):
        return self.client

class Contract(models.Model):
    client = models.ForeignKey(Client, on_delete=models.CASCADE, related_name='client_contracts')
    site_name = models.CharField(max_length=255)

    def __str__(self):
        return self.site_name

I can restrict the clients to the specific account managers by using the following view

class ClientListView(LoginRequiredMixin, ListView):
    model = Client
    template_name = "clients/list.html"

    def get_queryset(self, *args, **kwargs):
        return (
            super()
            .get_queryset(*args, **kwargs)
            .filter(account_manager__account_manager=self.request.user)
        )

However I can't seem to restrict the contracts to the account manager with the following view:

class AMContractDetailView(LoginRequiredMixin, DetailView):
    model = Contract
    template_name = 'contracts/am_contract_detail.html'

    def get_queryset(self, *args, **kwargs):
        return (
            super()
            .get_queryset(*args, **kwargs)
            .filter(client__account_manager=self.request.user.id)
        )

This allows account managers to see all the clients not just their own. I know I am doing something fundamentally wrong but have got a bit lost!

Any help would be appreciated.