HR diagram displaying the location of our programme Cepheid V470 Cas (red circle) and the other lithium-rich Cepheids described in the literature (blue circles). Evolutionary tracks are from Ekström et al. (2012) for 3−12 solar masses with and without rotation. The blue and red lines denote the blue and red boundaries of the IS for classic Cepheids (solid lines) and first-overtone Cepheids (dashed lines). Open circles indicate the positions of the lithium-rich non-variable supergiants.