The invention relates to a process for treating keratin fibres, in particular human keratin fibres such as the hair, comprising: (i) a step of applying an oxidized polysaccharide, (ii) a step of heating to a temperature of at least 100° C., (iii) a step of applying a compound (I) Ri—CHOH—CH(NH—COY)(CH20H) (I). The invention also relates to a cosmetic composition comprising an oxidized polysaccharide and a compound (I) for which Y═H and to kits. The process makes it possible to obtain good hair-conditioning cosmetic properties, with a long-lasting effect.
