The aim of this work is to show that organizational change is a response to certain problems generated by a market specialization strategy. Our study is based on two cases of SMEs that first engaged in a business relationship with a single client for more than five years. This led to a high degree of skills specialization and a certain organizational rigidity which was subsequently detrimental to the continuity of the company's activity, particularly when the relationship with the only single client was unexpectedly concluded, for the client had become increasingly demanding in terms of cost and time. Analysis of the data shows that both SMEs have made a series of organizational changes (restructuring of the company, recruitment of new skills, training activities, use of partnerships with other organizations, etc.) to overcome this perilous situation. As a consequence, these companies were able to reorient their business policy in order to reduce their dependence and then ensure their business sustainability and growth.