How to use the Func<Task<T>> Syntax?

I found this class in another answer Best way in .NET to manage queue of tasks on a separate (single) thread.

I wanted to try it out, but the syntax is a bit strange to me. Trying to just kick off a dummy task that returns a single int. I can't get this to compile, not sure what the syntax problem is.

        m_TaskQueue.Enqueue<int>(
                () => { return 1; }
            );

Compiler error:

Cannot convert lambda expression to delegate type System.Func<System.Threading.Tasks.Task<int>> because some of the return types in the block are not implicitly convertible to the delegate return type

Class from other answer:

public class TaskQueue
{
    private SemaphoreSlim semaphore;
    public TaskQueue()
    {
        semaphore = new SemaphoreSlim(1);
    }

    public async Task<T> Enqueue<T>(Func<Task<T>> taskGenerator)
    {
        await semaphore.WaitAsync();
        try
        {
            return await taskGenerator();
        }
        finally
        {
            semaphore.Release();
        }
    }
    public async Task Enqueue(Func<Task> taskGenerator)
    {
        await semaphore.WaitAsync();
        try
        {
            await taskGenerator();
        }
        finally
        {
            semaphore.Release();
        }
    }
}