Determine sequence contains no element using LINQ

Possible Duplicate:
LINQ: Max or Default?

I have some LINQ to filter DateTime vars.

List<DateTime> lst1 = new List<DateTime>();

 //.... add DataTime here

var d = lst1.Where(q => q <= DateTime.Now).Max();

And if I have no matched item the exceptions occurs.

I need to get empty d or at least null and I don't need exception here at all.

How do I can fix it?

Thank you!