Last names in JR Pass

Hi everyone,
I've found several posts about people -specially Spanish speaking countries- using only one last name in the JR Pass, but our passports include two of them (father's last name and mother's last name).
I'm going through something similar, so I'd really like to hear from you guys: Were you able to use your passes as they where, with only one last name? Did you need to return your vouchers and get them reissued?
Any advice is appreciated, thank you