diff --git a/utils.js b/utils.js
index ad08852..21b311b 100644
--- a/utils.js
+++ b/utils.js
@@ -207,7 +207,7 @@ function md5Str(data) {
 
 function sha1Str(data) {
   const hash = crypto.createHash('sha1');
-  return hash.update(data).digest('hex');
+  return hash.update(data).digest('hex').toLowerCase();
 }
 
 function getVal(obj, key, defVal = null) {