Within the framework of transverse-momentum-dependent factorization, we investigate for the first time the impact of a flavor-dependent intrinsic transverse momentum of quarks on the production of W bosons in proton-proton collisions at \sqrt{s} = 7 TeV. 
We estimate the shift in the extracted value of the W boson mass (M_W) induced by different choices of flavor-dependent parameters for the intrinsic quark transverse momentum by means of a template fit to the transverse-mass and the lepton transverse-momentum distributions of the W-decay products. 
We obtain -11 < \Delta M_W^+ < 4 MeV and -6 < \Delta M_W^- < 2 MeV with a statistical uncertainty of \pm  4 MeV. 
These findings call for more detailed investigations of flavor-dependent nonperturbative effects linked to the proton structure at hadron colliders.