C# Reflection Emit Call with parameter

I want to call a function with a parameter with the reflection.emit API. In the following is what I have at the moment. But when I run it, it throws the following exception: System.InvalidProgramException : Common Language Runtime detected an invalid program. So my question is what I have wrong in my code snippet below? Can someone help me out?

public class Test
{

    public void test()
    {
        Func<int, long> realSquareFunc = (val) => val * val;
        Type[] methodArgs = { typeof(int) };

        DynamicMethod squareIt = new DynamicMethod(
            "SquareIt",
            typeof(long),
            methodArgs,
            typeof(Test).Module)
        ;

        ILGenerator il = squareIt.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0); // Save parameter on stack
        il.Emit(OpCodes.Call, realSquareFunc.Method); // Call function with input as parameter
        il.Emit(OpCodes.Ret); // Return value from function call before

        var myMethod = (Func<int, long>)squareIt.CreateDelegate(realSquareFunc.GetType());
        var result = myMethod.Invoke(4); // Should be 16 (4*4)
    }

}