diff --git a/src/CartItem.php b/src/CartItem.php
index 0bf3a8d..675371b 100644
--- a/src/CartItem.php
+++ b/src/CartItem.php
@@ -412,7 +412,7 @@ class CartItem implements Arrayable, Jsonable
                 case 'priceTotal':
                     return round($this->priceNet * $this->qty, $decimals);
                 case 'subtotal':
-                    return round($this->priceTotal - $this->discountTotal, $decimals);
+                    return max(round($this->priceTotal - $this->discountTotal, $decimals), 0);
                 case 'priceTarget':
                     return round(($this->priceTotal - $this->discountTotal) / $this->qty, $decimals);
                 case 'taxTotal':
@@ -435,7 +435,7 @@ class CartItem implements Arrayable, Jsonable
                 case 'priceTotal':
                     return round($this->price * $this->qty, $decimals);
                 case 'subtotal':
-                    return round($this->priceTotal - $this->discountTotal, $decimals);
+                    return max(round($this->priceTotal - $this->discountTotal, $decimals), 0);
                 case 'priceTarget':
                     return round(($this->priceTotal - $this->discountTotal) / $this->qty, $decimals);
                 case 'taxTotal':