diff --git a/language/functions.xml b/language/functions.xml
index 5a8df8d6dc42..1148a25c65f1 100644
--- a/language/functions.xml
+++ b/language/functions.xml
@@ -1258,13 +1258,7 @@ class Cart
     
     public function add($product, $quantity)
     {
-        $this->products[$product] = $quantity;
-    }
-    
-    public function getQuantity($product)
-    {
-        return isset($this->products[$product]) ? $this->products[$product] :
-               FALSE;
+        $this->products[$product] = ($this->products[$product] ?? 0) + $quantity;
     }
     
     public function getTotal($tax)