diff --git a/addons/purchase/wizard/purchase_line_invoice.py b/addons/purchase/wizard/purchase_line_invoice.py
index 200778b6d70..c346560aa83 100644
--- a/addons/purchase/wizard/purchase_line_invoice.py
+++ b/addons/purchase/wizard/purchase_line_invoice.py
@@ -128,7 +128,7 @@ class purchase_line_invoice(osv.osv_memory):
                                 'property_account_expense_categ', 'product.category',
                                 context=context)
                     fpos = line.order_id.fiscal_position or False
-                    a = account_fiscal_obj.map_account(cr, uid, fpos, a)
+                    a = account_fiscal_obj.map_account(cr, uid, fpos, a).id
                     inv_id = invoice_line_obj.create(cr, uid, {
                         'name': line.name,
                         'origin': line.order_id.name,