C# Generics: Constraining T where T : Object doesn't compile; Error: Constraint cannot be special class 'object'

When I constrain T with : Object like this:

public interface IDoWork<T> where T : Object
{
    T DoWork();
}

I get the error:

Constraint cannot be special class 'object'

Does that mean there is an implied difference with the following that does compile?

public interface IDoWork<T> // where T : Object
{
    T DoWork();
}