[Context and motivation] Ensuring privacy of users’ data has become a top concern in software development, either to satisfy users’ needs or to comply with privacy laws. The problem may increase by the time a new law is in the vacancy period, and companies are working to understand how to comply with it. In addition, research has shown that many developers do not have sufficient knowledge about how to develop privacy-sensitive software. [Question/problem] Motivated by this scenario, this research investigates the personal factors affecting the developers’ understanding of privacy requirements during the vacancy period of a data protection law. [Principal ideas/results] We conducted thirteen interviews in six different private companies. As a result, we found nine personal factors affecting how software developers perceive and interpret privacy requirements. [Contribution] The identification of the personal factors contributes to the elaboration of effective methods for promoting proper privacy-sensitive software development. © 2020, Springer Nature Switzerland AG.