Kv10.1 is a voltage-gated potassium channel, whose upregulation can lead to severe developmental disorders and to cancer. Sánchez et al. found that in mammalian cells, Kv10.1 can localize to primary cilia, where it promotes cilia disassembly — a process that is thought to be required for mitosis. Accordingly, Kv10.1 knockdown increased cilia numbers and length, and this caused the hyperactivation of cilia-mediated Sonic hedgehog signalling, prolonged the cell cycle and forced mitosis in the presence of cilia. When implanted into mice, cells overexpressing Kv10.1 lacking the cilia-targeting motif had reduced tumorigenic potential compared to cells overexpressing the full-length protein, indicating that this previously unrecognized function of Kv10.1 in ciliogenesis is important for the pathologic effects associated with Kv10.1 misexpression.