This paper investigates how maintainability can be established in system integration (SI) projects where maintainers have no direct access to the source code of the third-party software being integrated. We propose a model for maintainability in SI focusing on postrelease activities, unlike traditional maintainability models where focus is on pre-release activities. Our model describes maintainability as a process characterized by ambiguity and negotiation that is supported through an infrastructure of debugging and coordination tools. Further, we describe how the process going from a software failure to establishing the fault causing the failure can be managed in SI. The results presented in this paper are based on observations from an ethnographic study of the Gentoo open source software (OSS) community, a large distributed volunteer community of over 320 developers developing and maintaining a software system for distributing and integrating third-party OSS software packages with different Unix versions.