diff --git a/partner-simplepay.js b/partner-simplepay.js
index 3d42cab..a3d85eb 100644
--- a/partner-simplepay.js
+++ b/partner-simplepay.js
@@ -199,7 +199,7 @@ function _responseBodyHandler(responseBody, task) {
 
 function getPartnerRCFromDiagMessage(diag) {
     let matches = diag.match(/^\s*\[(.*)\]/);
-    if (matches.length < 2) {
+    if (!matches || matches.length < 2) {
         return;
     }