diff --git a/openerp/addons/base/res/res_currency.py b/openerp/addons/base/res/res_currency.py
index 8a8067c6ff4..13bb14d0578 100644
--- a/openerp/addons/base/res/res_currency.py
+++ b/openerp/addons/base/res/res_currency.py
@@ -125,13 +125,9 @@ class res_currency(osv.osv):
         if not to_currency_id:
             to_currency_id = from_currency_id
 
-        context.update({'currency_rate_type_id': False})
-        if currency_rate_type_from:
-            context.update({'currency_rate_type_id': currency_rate_type_from})
-        if currency_rate_type_to:
-            context.update({'currency_rate_type_id': currency_rate_type_to})
-
+        context.update({'currency_rate_type_id': currency_rate_type_from})
         xc = self.browse(cr, uid, [from_currency_id], context=context)
+        context.update({'currency_rate_type_id': currency_rate_type_to})
         xc1 = self.browse(cr, uid, [to_currency_id], context=context)
         from_currency = (xc[0].id == from_currency_id and xc[0]) or xc[1]
         to_currency = (xc1[0].id == to_currency_id and xc1[0]) or xc1[1]