Bug: Generic Function that returns a Delegate from \-Expression

Hello List,
I experienced a bug with mono 1.9.1 x64/Linux. Compilation fails (it works 
with MS csc 3.5.21022.8). Source and gmcs output is attached.

$ ./gmcs --version
Mono C# compiler version 1.9.1.0

$ gcc --version
gcc (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu7)

Regards,
Simon Hengel

using System;
using System.Linq;
using System.Collections.Generic;

static class CurryBug
{	// curry for function of arity 3
	//
	// this compiles
	public static Func<int,Func<int, Func<int,int>>>
		curry_for_int_func (this Func<int,int,int,int> f)
	{
		return arg1 => arg2 => arg3 => f(arg1 , arg2 , arg3);
	}

	// but his does not
	static Func<A,Func<B,Func<C,D>>> curry<A,B,C,D> (this Func<A,B,C,D> f)