diff --git a/lib/apiserver/handler/on-received.js b/lib/apiserver/handler/on-received.js
index a6c8ffc..ab64ccb 100644
--- a/lib/apiserver/handler/on-received.js
+++ b/lib/apiserver/handler/on-received.js
@@ -32,7 +32,7 @@ module.exports = (req, res) => {
     const msgUpperCased = (msg || '').trim().toUpperCase();
     if (
         (msisdn.search(/\+*62/) === 0)
-        && blacklistMsgPatterns.find((pattern) => msgUpperCased.search(pattern))
+        && blacklistMsgPatterns.find((pattern) => msgUpperCased.search(pattern) >= 0)
     ) {
         logger.verbose('ON-RECEIVED 5486D373: Skip invalid message', {
             msg,