V−I versus I colour–magnitude diagram of Sculptor on which we superimpose the positions of the EMPS discussed in this paper. The photometry is taken from de Boer et al. (2011). The orange circles indicate our new sample of stars with chemical abundances derived from high-resolution spectroscopy. The star symbols identify the EMPS of Frebel et al. (2010a) and Simon et al. (2015), while the upright triangles show the sample of Tafelmeyer et al. (2010) and inverted triangles the EMPS of Starkenburg et al. (2013), which have not been reanalyzed at high resolution.