diff --git a/addons/account/account_move_line.py b/addons/account/account_move_line.py
index 478a3140d6f..a85bfd00316 100644
--- a/addons/account/account_move_line.py
+++ b/addons/account/account_move_line.py
@@ -947,7 +947,7 @@ class account_move_line(osv.osv):
 
             if field in ('amount_currency', 'currency_id'):
                 attrs.append('on_change="onchange_currency(account_id, amount_currency,currency_id, date, journal_id)"')
-                attrs.append("attrs='{'readonly':[('state','=','valid')]}'")
+                attrs.append('''attrs="{'readonly':[('state','=','valid')]}"''')
 
             if field in widths:
                 attrs.append('width="'+str(widths[field])+'"')