diff --git a/Gruntfile.js b/Gruntfile.js
index 94012f7bd949e1363cf8938759364743a4da6ac1..e5bb5e7bf522517d8495f4df670679e5ce9b8721 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -66,6 +66,7 @@ module.exports = grunt => {
             "--toc",
             `--toc-depth=${TOC_DEPTH}`,
             `--slide-level=${SLIDE_LEVEL}`,
+            "--variable=lang:fr-FR",
             `--variable=revealjs-url:${relative(dirname(pres), "./reveal.js")}`,
             "--variable=theme:irstea",
             "--variable=history:true",