As open source communities grow, they need to adapt to new dynamics: Different types of expertise between contributors, different expectations, etc. The arrival of a very large PR on the OpenFisca project became the test of the work we had put in to create a more resilient community. Since 2011, a community of developers and economists are developing OpenFisca, an open source framework in Python that turns law into software so it can be used by administrations, economists and activists. The contributors are split between tech experts and domain experts, each bringing interesting skills, mindsets and issues. However, a full time tech team became the full time core team, shifting the balance of the community. Having a full time team working on the project was a plus, but it gave tech experts a central role that put a lot of strain on domain experts’ contributions. In this talk, I will describe how we worked to create a dynamic community that can deal with uncertainty (new contributors, very large PRs, …) and grow to reach new heights in the hope it can inspire other communities.