StructureMap and Generics. How to specify default constructor?

I have a common interface:

public interface IRepository<T> { ... }

I have an implementation like this:

public class Repository<T> {
    public Repository<T>() { ... }
}

StructureMap (v 2.6.3) is configured as follows:

For(typeof(IRepository<>)).Use(typeof(Repository<>));

When I try to pull IRepository<Something>from StructureMap, I get Repository<Something>as expected. Hooray!

Now I have added a second constructor, and the implementation looks like this:

public class Repository<T> {
    public Repository<T>() { ... }
    public Repository<T>(string database) { ... }
} 

When I try to get IRepository<Something>now, I get an exception, because by default it tries to use the new constructor with a parameter. Boo!

How do I reconfigure StructureMap so that it knows what to use the constructor without parameters?