Minn. Stat. § 322.05
The surname of a limited partner shall not appear in the partnership name, unless:
(2) prior to the time when the limited partner became such the business had been carried on under a name in which that partner's surname appeared.
A limited partner whose name appears in a partnership name contrary to the provisions of this section is liable as a general partner to partnership creditors who extend credit to the partnership without actual knowledge that the limited partner is not a general partner.