diff --git a/lib/partner-listener/routers/topup.js b/lib/partner-listener/routers/topup.js
index f157a30..f9f8fba 100644
--- a/lib/partner-listener/routers/topup.js
+++ b/lib/partner-listener/routers/topup.js
@@ -33,7 +33,8 @@ function onInvalidParameter(missingParameter, req, res) {
 function pagePrerequisite(req, res, next) {
     if (!req.body) req.body = {};
 
-    if (!req.body.terminal_name && !req.query.terminal_name) {
+    const terminalName = req.body.terminal_name || req.query.terminal_name;
+    if (!terminalName || typeof terminalName !== 'string') {
         onInvalidParameter('terminal_name', req, res);
         return;
     }