diff --git a/ci/prepare_squashfs.sh b/ci/prepare_squashfs.sh
index 8691f0518f0b784565264575561e6a9c0281cac4..934bdcf0b684a0fdfbf1f93a563aef84e06c47ac 100755
--- a/ci/prepare_squashfs.sh
+++ b/ci/prepare_squashfs.sh
@@ -21,7 +21,7 @@ then
     then
         echo "No default branch ($squash_base) squashfs found"
         echo "Creating an empty one"
-        empty=(mktemp -d)
+        empty=$(mktemp -d)
         sqfs_base_image=/squashfs-cache/${stack}-${environment}-${squash_base}-initial.sqfs
         mksquashfs ${empty} ${sqfs_base_image}
     else