diff --git a/partner-otomax.js b/partner-otomax.js
index 0e4674e..204bf39 100644
--- a/partner-otomax.js
+++ b/partner-otomax.js
@@ -119,6 +119,9 @@ function parseMessage(task, message) {
     else if (message.indexOf('GAGAL') >= 0) {
         rc = '40';
     }
+    else if (message.indexOf('Invalid Signature') >= 0) {
+        rc = '40';
+    }
 
     callbackReport(task.requestId, rc, message);
 }