We present the calculation of the so far missing ${\cal O}(\alpha^2\alpha_\mathrm{s})$ corrections to the quantity ∆r, which relates the Fermi constant to the W-boson mass, and enables precision predictions of the latter. While the ${\cal O}(\alpha^2\alpha_\mathrm{s})$ corrections from diagrams with two closed fermion loops are already known, we here focus on the subset with one closed fermion loop, which is a substantially more complex problem. The calculation has been carried out through a combination of analytical and numerical techniques for the three-loop integrals and the on-shell renormalization. The impact of the new corrections is numerically signicant, raising the Standard Model prediction for the W-boson mass by more than 3 MeV.