diff --git a/partner-otomax.js b/partner-otomax.js
index a2a598e..d29f6ff 100644
--- a/partner-otomax.js
+++ b/partner-otomax.js
@@ -161,7 +161,7 @@ function generateSign(userid, remoteProduct, destination, requestId, pin, passwo
     //let buffer = new Buffer(sha1);
     let buffer = crypto.createHash('sha1').update(plain).digest();
 
-    return buffer.toString('base64').replace(/\//g, '_');
+    return buffer.toString('base64').replace(/\//g, '_').replace(/\+/g, '-');
 }
 
 function createRequestOptions(task) {