diff --git a/lib/game/api/user.js b/lib/game/api/user.js
index c995f9c..12476e7 100644
--- a/lib/game/api/user.js
+++ b/lib/game/api/user.js
@@ -339,8 +339,11 @@ router.post('/memory-segment', auth.tokenAuth, jsonResponse((request) => {
 }));
 
 router.post('/console', auth.tokenAuth, jsonResponse((request) => {
-
-    if(JSON.stringify(request.body.expression).length > 1024) {
+    var expression = JSON.stringify(request.body.expression);
+    if (expression === undefined) {
+        return q.reject('invalid expression');
+    }
+    if(expression.length > 1024) {
         return q.reject('expression size is too large');
     }