Example SEDs of galaxies at 3.5 < z < 4.5 with M > 10^10.5 M_⊙ and M₁₄₀₀ > −18.5. Their SEDs, especially in the IRAC bands, indicate that they are really massive objects at high redshift and that the nebular contribution is not dominant. The objects ID = 8785 and 17 749 are quite old (age /τ ≥ 8), while ID = 4466 and 13299 have E(B − V) ≥ 0.4. All these galaxies are characterized by very red colours, and thus cannot be selected by standard LBG selection criteria based on UV rest-frame colours. Because of their large masses, however, they represent a relatively rare population, which can contribute significantly to the high-mass tail of the mass function at z = 4.