Foreach can throw an InvalidCastException?

Imagine the following code:

class foreach_convert
{
    public static void method2()
    {
        List<IComparable> x = new List<IComparable>();
        x.Add(5);

        foreach (string s in x)
        {
            //InvalidCastException in runtime
        }
    }
}

I wonder, why is this foreach behavior so... not C#-like? What happens here is an implicit cast to a subclass, which is error-prone and seems to be banned in every other place in the language. Or am I not right?

P.S. The reason I'm asking is that I had a bug in the similar code in my project, where I used to iterate through a custom Collection from an external library, which was called like SomeTypeCollection, but in fact provided a collection of base type items and could have contained items of SomeOtherType. My fault, but still neither the language, nor the compiler provided any explicit hints/warnings, which is quite unusual for C#...