diff --git a/src/CartItem.php b/src/CartItem.php
index 5a49ef2..667bedc 100644
--- a/src/CartItem.php
+++ b/src/CartItem.php
@@ -98,7 +98,7 @@ class CartItem implements Arrayable, Jsonable
         if (strlen($price) < 0 || !is_numeric($price)) {
             throw new \InvalidArgumentException('Please supply a valid price.');
         }
-        if (strlen($price) < 0 || !is_numeric($weight)) {
+        if (strlen($weight) < 0 || !is_numeric($weight)) {
             throw new \InvalidArgumentException('Please supply a valid weight.');
         }