diff --git a/modules/account_invoice/invoice.py b/modules/account_invoice/invoice.py
index f9e023e..774b3b0 100755
--- a/modules/account_invoice/invoice.py
+++ b/modules/account_invoice/invoice.py
@@ -1890,8 +1890,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
         cls._check_taxes(invoices)
         # cls._check_similar(invoices)
 
-        invoices_in = cls.browse([i for i in invoices if i.type == 'in'])
-        cls.set_number(invoices_in)
+        cls.set_number(invoices)
         cls._store_cache(invoices)
         
         moves = []
diff --git a/modules/account_invoice/tests/test_module.py b/modules/account_invoice/tests/test_module.py
index ef331c6..dfe5702 100755
--- a/modules/account_invoice/tests/test_module.py
+++ b/modules/account_invoice/tests/test_module.py
@@ -290,5 +290,32 @@ class AccountInvoiceTestCase(
         clean_moves.assert_called_once_with([move])
         save_invoices.assert_called()
 
+    @with_transaction()
+    def test_validate_invoice_sets_number_for_customer_invoice(self):
+        'validating customer invoices now assigns the invoice number'
+        Invoice = Pool().get('account.invoice')
+
+        move = Mock()
+        invoice = Invoice()
+        invoice.type = 'out'
+        invoice.move = None
+        invoice.get_move = Mock(return_value=move)
+        invoice.do_lot_invoicing = Mock()
+
+        move_model = Mock()
+
+        with patch.object(Invoice, '_check_taxes'), patch.object(
+                Invoice, '_store_cache'), patch.object(
+                Invoice, 'set_number') as set_number, patch.object(
+                Invoice, 'cleanMoves'), patch.object(
+                Invoice, 'save'), patch(
+                'trytond.modules.account_invoice.invoice.Pool'
+                ) as PoolMock:
+            PoolMock.return_value.get.return_value = move_model
+
+            Invoice.validate_invoice([invoice])
+
+        set_number.assert_called_once_with([invoice])
+
 
 del ModuleTestCase