Software product innovation in large organizations is fundamentally chal-lenging because of restrained freedom and flexibility to conduct experi-ments. As a response, large agile companies form internal startups to initiate employ-driven innovation, inspired by Lean startup. This case study investi-gates how communities of practice support five internal startups in develop-ing new software products within a large organization. We observed six communities of practice meetings, two workshops and conducted ten semi-structured interviews over the course of a year. Our findings show that a community of practice, called the Innovation guild, allowed internal startups to help each other by collectively solving problems, creating shared practic-es, and sharing knowledge. This study confirms that benefits documented in earlier research into CoPs also hold true in the context of software product innovation in large organizations. Henceforth, we suggest that similar innova-tion guilds, as described in this paper, can support large companies in the in-novation race for new software products.