diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
index 410e934ab71..1a7ffc3c339 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
@@ -1755,6 +1755,9 @@ class SalesInvoice(SellingController):
 
 	def update_project(self):
 		unique_projects = list(set([d.project for d in self.get("items") if d.project]))
+		if self.project and self.project not in unique_projects:
+			unique_projects.append(self.project)
+
 		for p in unique_projects:
 			project = frappe.get_doc("Project", p)
 			project.update_billed_amount()
diff --git a/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
index d2b8882743a..57eb84caaa4 100644
--- a/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
@@ -4217,6 +4217,20 @@ class TestSalesInvoice(FrappeTestCase):
 		self.assertTrue(jv)
 		self.assertEqual(jv[0], si.grand_total)
 
+	def test_total_billed_amount(self):
+		si = create_sales_invoice(do_not_submit=True)
+
+		project = frappe.new_doc("Project")
+		project.project_name = "Test Total Billed Amount"
+		project.save()
+
+		si.project = project.name
+		si.save()
+		si.submit()
+
+		doc = frappe.get_doc("Project", project.name)
+		self.assertEqual(doc.total_billed_amount, si.grand_total)
+
 
 def set_advance_flag(company, flag, default_account):
 	frappe.db.set_value(