diff --git a/src/middleware/staticFileServingAndDirectoryListings.js b/src/middleware/staticFileServingAndDirectoryListings.js
index 2f4e8b0..bea1530 100644
--- a/src/middleware/staticFileServingAndDirectoryListings.js
+++ b/src/middleware/staticFileServingAndDirectoryListings.js
@@ -162,7 +162,7 @@ module.exports = (req, res, logFacilities, config, next) => {
           try {
             let rhd = config.getCustomHeaders();
             rhd["Accept-Ranges"] = "bytes";
-            rhd["Content-Range"] = "bytes */" + filelen;
+            rhd["Content-Range"] = `bytes */${filelen}`;
             const regexmatch = req.headers["range"].match(
               /bytes=([0-9]*)-([0-9]*)/,
             );