diff --git a/openerp/addons/base/ir/ir_attachment.py b/openerp/addons/base/ir/ir_attachment.py
index c096056426b..c0bd7198a1a 100644
--- a/openerp/addons/base/ir/ir_attachment.py
+++ b/openerp/addons/base/ir/ir_attachment.py
@@ -248,6 +248,8 @@ class ir_attachment(osv.osv):
         mimetype = 'application/octet-stream'
         if values.get('datas_fname'):
             mimetype = mimetypes.guess_type(values['datas_fname'])[0]
+        if values.get('url'):
+            mimetype = mimetypes.guess_type(values['url'])[0]
         if values.get('datas') and (not mimetype or mimetype == 'application/octet-stream'):
             mimetype = guess_mimetype(values['datas'].decode('base64'))
         return mimetype