diff --git a/src/CartItem.php b/src/CartItem.php
index 0717ed7..e5ac8ac 100644
--- a/src/CartItem.php
+++ b/src/CartItem.php
@@ -97,6 +97,9 @@ class CartItem implements Arrayable, Jsonable
         if (strlen($price) < 0 || !is_numeric($price)) {
             throw new \InvalidArgumentException('Please supply a valid price.');
         }
+        if (strlen($weight) < 0 || !is_numeric($weight)) {
+            throw new \InvalidArgumentException('Please supply a valid weight.');
+        }
 
         $this->id = $id;
         $this->name = $name;