Worker cooperatives emerged as collective good producers in the gig economy, by providing their membership with more secure working conditions that may especially be in demand during crises. Even under normal conditions, cooperatives with a heterogeneous membership would be vulnerable to opportunistic member behaviour depleting collective resources. This raises the question of how such cooperatives design rules to address opportunism and whether rules evolve in the face of external shocks. We study the case of gig workers’ cooperative Smart Belgium between 2017 and 2022, thereby covering the COVID-19 pandemic as an external shock. Building on the institutional grammar methodology, we analyse 412 rules of Smart. The findings indicate that external shocks with sudden resource scarcity (COVID-19) do not necessarily motivate rule changes while external shocks without an effect on collective resources (new national legislation) can motivate rule changes. The study also provides support for the notion that cooperatives with a heterogeneous membership design rules to mitigate opportunism.