diff --git a/erpnext/manufacturing/doctype/blanket_order/blanket_order.py b/erpnext/manufacturing/doctype/blanket_order/blanket_order.py
index 5381abf..822c7fc 100644
--- a/erpnext/manufacturing/doctype/blanket_order/blanket_order.py
+++ b/erpnext/manufacturing/doctype/blanket_order/blanket_order.py
@@ -4,6 +4,7 @@
 
 from __future__ import unicode_literals
 import frappe
+from frappe.utils import flt
 from frappe.model.document import Document
 from frappe.model.mapper import get_mapped_doc
 from erpnext.stock.doctype.item.item import get_item_defaults
@@ -28,7 +29,8 @@
 @frappe.whitelist()
 def make_sales_order(source_name):
 	def update_item(source, target, source_parent):
-		target.qty = source.get("qty") - source.get("ordered_qty")
+		target_qty = source.get("qty") - source.get("ordered_qty")
+		target.qty = target_qty if not flt(target_qty) < 0 else 0
 		item = get_item_defaults(target.item_code, source_parent.company)
 		if item:
 			target.item_name = item.get("item_name")
@@ -53,7 +55,8 @@
 @frappe.whitelist()
 def make_purchase_order(source_name):
 	def update_item(source, target, source_parent):
-		target.qty = source.get("qty") - source.get("ordered_qty")
+		target_qty = source.get("qty") - source.get("ordered_qty")
+		target.qty = target_qty if not flt(target_qty) < 0 else 0
 		item = get_item_defaults(target.item_code, source_parent.company)
 		if item:
 			target.item_name = item.get("item_name")
diff --git a/erpnext/manufacturing/doctype/blanket_order/test_blanket_order.js b/erpnext/manufacturing/doctype/blanket_order/test_blanket_order.js
new file mode 100644
index 0000000..51a0d94
--- /dev/null
+++ b/erpnext/manufacturing/doctype/blanket_order/test_blanket_order.js
@@ -0,0 +1,23 @@
+/* eslint-disable */
+// rename this file from _test_[name] to test_[name] to activate
+// and remove above this line
+
+QUnit.test("test: Blanket Order", function (assert) {
+	let done = assert.async();
+
+	// number of asserts
+	assert.expect(1);
+
+	frappe.run_serially([
+		// insert a new Blanket Order
+		() => frappe.tests.make('Blanket Order', [
+			// values to be set
+			{key: 'value'}
+		]),
+		() => {
+			assert.equal(cur_frm.doc.key, 'value');
+		},
+		() => done()
+	]);
+
+});