A transparent substrate is provided, on a main face, with a stack of thin layers including at least one, metallic functional layer having properties of reflection in the infrared region and/or in the solar radiation region, based on silver or on silver-containing metal alloy, and two antireflective coatings. The antireflective coatings each include at least one dielectric layer. The functional layer is positioned between the two antireflective coatings. At least one nickel oxide NixO layer is located under the functional layer in the direction of the substrate and/or above the functional layer, with interposition of at least one layer or of just one layer made of a different material between the or each nickel oxide NixO layer and the functional layer.