diff --git a/addons/account/account_move_line.py b/addons/account/account_move_line.py
index ebecc8c24a4..89268d68148 100644
--- a/addons/account/account_move_line.py
+++ b/addons/account/account_move_line.py
@@ -923,7 +923,7 @@ class account_move_line(osv.osv):
                         'name': vals['name'],
                         'date': vals.get('date', time.strftime('%Y-%m-%d')),
                         'account_id': vals.get('analytic_account_id', False),
-                        'unit_amount':'quantity' in vals and vals['quantity'] or 1.0,
+                        'unit_amount': vals.get('quantity', 1.0),
                         'amount': vals.get('debit', 0.0) or vals.get('credit', 0.0),
                         'general_account_id': vals['account_id'],
                         'journal_id': journal.analytic_journal_id.id,