IEqualityComparer for subclasses

I would like to implement an IEqualityComparer<A> where A is a superclass of B, C and D. Then I would like to use the same equality comparer to compare lists of objects of classes B, C and D.

However, this does not seem to be possible. The compiler complains that IEqualityComparer<A> cannot be converted to IEqualityComparer<B>.

I solved the problem using generic classes. However, this seems somewhat overly complicated. Is there a simple way of achieving this elegantly (like some kind of an implicit cast)?