diff --git a/cart-grain.go b/cart-grain.go
index ec03340..0454596 100644
--- a/cart-grain.go
+++ b/cart-grain.go
@@ -293,7 +293,7 @@ func (c *CartGrain) HandleMessage(message *Message, isReplay bool) (*FrameWithPa
 		} else {
 			for i, item := range c.Items {
 				if item.Id == int(msg.Id) {
-					if item.Quantity <= int(msg.Quantity) {
+					if msg.Quantity <= 0 {
 						c.TotalPrice -= item.Price * int64(msg.Quantity)
 						c.Items = append(c.Items[:i], c.Items[i+1:]...)
 					} else {