A wealth of research has suggested that emotions play a significant role in creative problem solving, but less work has focused on investigating their roles in design. This is surprising given that creative problem solving lies at the heart of the design process. In an exploratory study we interviewed 9 expert designers about their emotions during the design process. We identified several relevant emotions and extended Wallas model of creative problem solving with emotional components for each of its stages. We also identified ways in which expert designers regulate their emotions and concluded with a discussion of the contributions of our work for design methods and tools, design thinking and design expertise.