diff --git a/index.js b/index.js
index ee0888b..8132b14 100644
--- a/index.js
+++ b/index.js
@@ -132,7 +132,9 @@ exports.report = async (data, xid, retry) => {
         info: data.info,
         detail: data.detail,
         data: data.data,
-        struk: data.struk,
+        struk: (typeof data.struk === 'string' && data.struk)
+            || (data.struk && JSON.stringify(data.struk))
+            || null,
     };
 
     logger.verbose('POSTPAID2-SDK: Going to report to CORE', {