diff --git a/openerp/addons/base/res/res_currency.py b/openerp/addons/base/res/res_currency.py
index 13bb14d0578..495a931f91d 100644
--- a/openerp/addons/base/res/res_currency.py
+++ b/openerp/addons/base/res/res_currency.py
@@ -103,41 +103,51 @@ class res_currency(osv.osv):
     def is_zero(self, cr, uid, currency, amount):
         return abs(self.round(cr, uid, currency, amount)) < currency.rounding
 
-    def _get_conversion_rate(self, cr, uid, from_currency, to_currency, context=None):
+    def _get_conversion_rate(self, cr, uid, from_currency_rate, to_currency_rate, context=None):
         if context is None:
             context = {}
-        if from_currency['rate'] == 0 or to_currency['rate'] == 0:
+        if from_currency_rate == 0 or to_currency_rate == 0:
             date = context.get('date', time.strftime('%Y-%m-%d'))
-            if from_currency['rate'] == 0:
-                currency_symbol = from_currency.symbol
+            if from_currency_rate == 0:
+                currency_symbol = context.get('from_curr_symbol')
             else:
-                currency_symbol = to_currency.symbol
+                currency_symbol = context.get('to_curr_symbol')
             raise osv.except_osv(_('Error'), _('No rate found \n' \
                     'for the currency: %s \n' \
                     'at the date: %s') % (currency_symbol, date))
 
-        return to_currency.rate/from_currency.rate
+        return to_currency_rate/from_currency_rate
 
     def compute(self, cr, uid, from_currency_id, to_currency_id, from_amount,
                 round=True, currency_rate_type_from=False, currency_rate_type_to=False, context=None):
+        if not context:
+            context = {}
         if not from_currency_id:
             from_currency_id = to_currency_id
         if not to_currency_id:
             to_currency_id = from_currency_id
 
-        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)
+        ctx1 = context.copy()
+        ctx1.update({'currency_rate_type_id': currency_rate_type_from})
+        xc = self.browse(cr, uid, [from_currency_id], context=ctx1)
         from_currency = (xc[0].id == from_currency_id and xc[0]) or xc[1]
+        from_currency_rate = from_currency['rate']
+        context.update({'from_curr_symbol': from_currency.symbol})
+
+        ctx2 = context.copy()
+        ctx2.update({'currency_rate_type_id': currency_rate_type_to})
+        xc1 = self.browse(cr, uid, [to_currency_id], context=ctx2)
         to_currency = (xc1[0].id == to_currency_id and xc1[0]) or xc1[1]
+        to_currency_rate = to_currency['rate']
+        context.update({'to_curr_symbol': to_currency.symbol})
+
         if to_currency_id == from_currency_id:
             if round:
                 return self.round(cr, uid, to_currency, from_amount)
             else:
                 return from_amount
         else:
-            rate = self._get_conversion_rate(cr, uid, from_currency, to_currency, context=context)
+            rate = self._get_conversion_rate(cr, uid, from_currency_rate, to_currency_rate, context=context)
             if round:
                 return self.round(cr, uid, to_currency, from_amount * rate)
             else: