Spectra of Sher 25 and of five NGC 3603 bona-fide O-type cluster stars in the region of the two deep and narrow diffuse interstellar bands (DIBs) λ5780 and 5797 Å (see the legend). Other DIBs in this wavelength range are the shallow but broad λ5778 Å feature and the narrow and shallow λλ5766, 5772, 5776, 5793, 5795, and 5809 Å features. The variation of the different spectra in the red is due to the different appearance of the stellar CIV λ5801 and 5812 Å lines in the O-type stars. The spectrum of Sher 25 was artificially downgraded in resolution to match the lower R = 5800 of the FLAMES/GIRAFFE data.