diff --git a/erpnext/selling/page/point_of_sale/point_of_sale.js b/erpnext/selling/page/point_of_sale/point_of_sale.js
index 726e80f..6601b9f 100644
--- a/erpnext/selling/page/point_of_sale/point_of_sale.js
+++ b/erpnext/selling/page/point_of_sale/point_of_sale.js
@@ -222,6 +222,11 @@
 	}
 
 	update_item_in_frm(item, field, value) {
+		if (field == 'qty' && value < 0) {
+			frappe.msgprint(__("Quantity must be positive"));
+			value = item.qty;
+		}
+
 		if (field) {
 			frappe.model.set_value(item.doctype, item.name, field, value);
 		}