Motivated by the recent work of Brzemi\'nski, Motyka, Sadzikowski and Stebel
in arXiv:1611.04449, where forward Drell--Yan production is studied in
proton-proton collisions at the LHC, we improve their calculation by
introducing an unintegrated gluon density obtained in arXiv:1209.1353 and
arXiv:1301.5283 from a fit to combined HERA data at small values of Bjorken
x. This gluon density was calculated within the BFKL formalism at
next-to-leading order with collinear corrections. We show that it generates a
good description of the forward Drell--Yan cross section dependence on the
invariant mass of the lepton pair both for LHCb and ATLAS data.Comment: 11 pages with 5 figure