Gas-phase C/O ratio as a function of time and distance to the star for the two different values of the stellar mass (M_∗= 1, 0.1 M_⊙) and three values of the turbulent viscosity (α = 10⁻², 10⁻³, 10⁻⁴). The sublimation lines of the main species contributing to the C/O ratio are indicated with vertical lines, similar to Fig. 1. The solid and dash-dotted contours respectively indicate [C/O]_gas = 1 and the stellar value [C/O]_gas = 0.55, above (resp. below) which the gas-phase C/O can be described as super-stellar (resp. sub-stellar). The shaded area indicates that the total mass of solids in the disc has decreased below 5% of its initial value, marking the advanced depletion of the disc material. Similar to Fig. 5, we see that the gas-phase C/O ratio can be greater than unity (and often super-stellar) in different regions of the disc for most of the disc lifetime.