Can Spring JPA projections have Collections?

I have a Customer entity from which I only want to select a few fields and their associated CustomerAddresses. I've defined a Spring Data JPA projection interface as follows:

public interface CustomerWithAddresses {
    Integer getId();
    String getFirstName();
    String getLastName();
    String getBrandCode();
    String getCustomerNumber();
    Set<CustomerAddress> getCustomerAddresses();
}

But from my Repository method:

CustomerWithAddresses findCustomerWithAddressesById(@Param("id") Integer id);

I keep getting NonUniqueResultException for Customers with multiple CustomerAddresses. Do projections have to have a flat structure, i.e. they don't support Collections the same way true Entities do?