diff --git a/addons/thunderbird/installer.py b/addons/thunderbird/installer.py
index 5bf11218842..35d31b9d636 100644
--- a/addons/thunderbird/installer.py
+++ b/addons/thunderbird/installer.py
@@ -41,7 +41,7 @@ class thunderbird_installer(osv.osv_memory):
         'pdf_name':fields.char('File name', size=64),
         'thunderbird':fields.boolean('Thunderbird Plug-in', help="Allows you to select an object that you would like to add to your email and its attachments."),
         'plugin_file':fields.binary('Thunderbird Plug-in', readonly=True, help="Thunderbird plug-in file. Save as this file and install this plug-in in thunderbird."),
-        'pdf_file':fields.char('Installation Manual', size="264", help="The documentation file :- how to install Thunderbird Plug-in.", readonly=True),
+        'pdf_file':fields.char('Installation Manual', size=264, help="The documentation file :- how to install Thunderbird Plug-in.", readonly=True),
         'description':fields.text('Description', readonly=True)
     }