diff --git a/partner-kospinjasa.js b/partner-kospinjasa.js
index cc20d9d..fbaf8db 100644
--- a/partner-kospinjasa.js
+++ b/partner-kospinjasa.js
@@ -72,7 +72,7 @@ function topupRequest(task, retry) {
 function createSignature(args, password) {
     var passwordHash = crypto.createHash('sha256').update(password).digest().toString('hex');
 
-    var result = crypto.createHash('sha1').update(
+    var plain =
         args.userName
         + passwordHash
         + args.productCode
@@ -80,12 +80,13 @@ function createSignature(args, password) {
         + args.transactionType
         + args.billNumber
         + args.amount
-        + args.ref
-        + args.timestamp
-    ).digest().toString('hex');
+        + args.reff
+        + args.timeStamp;
+
+    var result = crypto.createHash('sha1').update(plain).digest().toString('hex');
 
     if (logger) {
-        logger.verbose('Calculating signature', {result: result, args: args});
+        logger.verbose('Calculating signature', {plain: plain, result: result, args: args});
     }
 
     return result;