diff --git a/is-clean.sh b/is-clean.sh
index 27625702f..b50600b68 100755
--- a/is-clean.sh
+++ b/is-clean.sh
@@ -15,7 +15,7 @@ fi
 
 branch="$(git rev-parse --abbrev-ref HEAD)"
 
-if [ $branch != "master" && $branch != "test" ]; then
+if [[ $branch != "master" && $branch != "test" ]]; then
     echo "Not on master or test" >&2
     exit 1
 fi