diff --git a/modules/purchase/purchase.py b/modules/purchase/purchase.py
index 6f442ac..99cc600 100755
--- a/modules/purchase/purchase.py
+++ b/modules/purchase/purchase.py
@@ -1891,6 +1891,8 @@ class Line(sequence_ordered(), ModelSQL, ModelView):
                         self.product.supplier_taxes_deductible_rate_used)
                 invoice_line.invoice_type = 'in'
                 if self.product:
+                    if self.product.type == 'service':
+                        quantity = 1
                     if self.product.type == 'service' and not self.product.landed_cost:
                         invoice_line.account = self.product.account_stock_in_used
                     else: