diff --git a/addons/sale/sale.py b/addons/sale/sale.py
index 1244cf09f5f..be4e4a01e1d 100644
--- a/addons/sale/sale.py
+++ b/addons/sale/sale.py
@@ -151,13 +151,12 @@ class sale_order(osv.osv):
         sale_clause = ''
         no_invoiced = False
         for arg in args:
-            if arg[1] == '=':
-                if arg[2]:
-                    clause += 'AND inv.state = \'paid\''
-                else:
-                    clause += 'AND inv.state != \'cancel\' AND sale.state != \'cancel\'  AND inv.state <> \'paid\'  AND rel.order_id = sale.id '
-                    sale_clause = ',  sale_order AS sale '
-                    no_invoiced = True
+            if (arg[1] == '=' and arg[2]) or (arg[1] == '!=' and not arg[2]):
+                clause += 'AND inv.state = \'paid\''
+            else:
+                clause += 'AND inv.state != \'cancel\' AND sale.state != \'cancel\'  AND inv.state <> \'paid\'  AND rel.order_id = sale.id '
+                sale_clause = ',  sale_order AS sale '
+                no_invoiced = True
 
         cursor.execute('SELECT rel.order_id ' \
                 'FROM sale_order_invoice_rel AS rel, account_invoice AS inv '+ sale_clause + \