diff --git a/ServiceAPI/Apps.php b/ServiceAPI/Apps.php
index 521b117e..6504c23e 100644
--- a/ServiceAPI/Apps.php
+++ b/ServiceAPI/Apps.php
@@ -54,6 +54,11 @@ class Apps implements Handler
             $reject("No application with this id found");
             return;
         }
+
+        if($amount < 0) {
+            $reject(552, "Payment amount is invalid");
+            return;
+        }
         
         $coinsLeft = $this->user->getCoins() - $amount;
         if($coinsLeft < 0) {
diff --git a/Web/static/js/al_games.js b/Web/static/js/al_games.js
index 78bd738c..63994b83 100644
--- a/Web/static/js/al_games.js
+++ b/Web/static/js/al_games.js
@@ -142,6 +142,8 @@ function handlePayment(event) {
             ok: false,
             error: "negative sum"
         }, '*');
+        
+        return;
     }
 
     MessageBox(