Service-oriented architecture (SOA) brings new perspectives not only to software architecture but also to enterprise business processes. SOA promotes the use of loosely coupled services to automate business processes. The automation of business processes raises several challenges for enterprises. One of those challenges relates to the maintenance of business processes, more precisely how to facilitate changes within existing business processes, possibly even at run-time. Furthermore, changing a collaborative business process can have an impact on the contract specified between the parties involved. Thus, a business process may need to adapt to meet a new contract. Some approaches propose solutions to support business process adaptability; however, they do not handle adaptability in the context of multi-partner collaborative business processes. In this paper, we propose a new approach to support adaptability for such collaborative processes. This approach uses a protocol, called Change Protocol for Collaboration (CPC), for managing the changes that can have incidence on the contract.