diff --git a/slides/gen_index.sh b/slides/gen_index.sh
index c92d88bcfef7065030d3ee6d47072872ccd1b8b8..5ecece660e8a02222c9c5d85e270a2f9f1b4b427 100755
--- a/slides/gen_index.sh
+++ b/slides/gen_index.sh
@@ -44,7 +44,7 @@ done
 IFS=$'\n'
 classes=($(sort <<<"${classes[*]}"))
 date=$(date '+%Y-%m-%d')
-echo "---" >> index.md
+echo "---" > index.md
 echo "title: Cours de programmation séquentielle" >> index.md
 echo "date: ${date}" >> index.md
 echo "---" >> index.md