However, on 25 June, it was announced that due to the expected landslide resulting in the closure of the Chambon tunnel on the Briançon-Grenoble road, the route of stage 20 would be changed, bypassing the Col du Galibier. Instead of using the Télégraphe, the riders would continue along the valley to Saint-Jean-de-Maurienne rather than Saint-Michel-de-Maurienne, where they would start the long Hors catégorie Col de la Croix de Fer. The climb was used for the second day in a row, although a different side was used. This one is less steep, averaging 5.2%. From there, the peloton used the route of stage 18's ascent as a descent towards Le Bourg-d'Oisans, where the planned intermediate sprint was held, before the Alpe d'Huez, also as scheduled. The distance of the stage remained intact.