The invention relates to a substrate (1) provided with a thin-film multilayer comprising an alternation of n functional layers (3) having reflection properties in the infrared and/or in solar radiation, and (n+1) coatings (2, 5), where n≧1, said coatings being composed of a layer or a plurality of layers (2a, 2b, 5a, 5b), characterized in that, in order to preserve the optical and/or mechanical quality of the multilayer in the case in which the substrate (1) provided with said multilayer is subjected to a heat treatment of the toughening, bending or annealing type, at least one of the functional layers (3) includes a blocker coating (4) consisting of: on the one hand, a “protection” layer made of a material capable of helping to protect the functional layer from oxidizing and/or nitriding attack, immediately in contact with said functional layer; and on the other hand, at least one “adhesion” layer made of a material capable of promoting adhesion, immediately in contact with said “protection” layer.