diff --git a/addons/mail/ir_attachment.py b/addons/mail/ir_attachment.py
index 99c5a9e054e..a5d8705c0fb 100644
--- a/addons/mail/ir_attachment.py
+++ b/addons/mail/ir_attachment.py
@@ -186,12 +186,11 @@ class IrAttachment(osv.Model):
     def get_attachment_type(self, cr, uid, ids, name, args, context=None):
         result = {}
         for attachment in self.browse(cr, uid, ids, context=context):
-            fileext = os.path.splitext(attachment.datas_fname)[1].lower()
-            if not fileext or not fileext[1:] in self._fileext_to_type:
-                return 'unknown'
-            result[attachment.id] = self._fileext_to_type[fileext[1:]]
+            fileext = os.path.splitext(attachment.datas_fname or '')[1].lower()[1:]
+            result[attachment.id] = self._fileext_to_type.get(fileext, 'unknown')
         return result
 
     _columns = {
-        'file_type': fields.function(get_attachment_type, type='char', string='File Type'),
+        'file_type_icon': fields.function(get_attachment_type, type='char', string='File Type Icon'),
+        'file_type': fields.related('file_type_icon', type='char'),     # FIXME remove in trunk
     }
diff --git a/addons/mail/mail_message.py b/addons/mail/mail_message.py
index 40a51df91d2..4c05d7a6d1f 100644
--- a/addons/mail/mail_message.py
+++ b/addons/mail/mail_message.py
@@ -351,12 +351,12 @@ class mail_message(osv.Model):
         partner_tree = dict((partner[0], partner) for partner in partners)
 
         # 2. Attachments as SUPERUSER, because could receive msg and attachments for doc uid cannot see
-        attachments = ir_attachment_obj.read(cr, SUPERUSER_ID, list(attachment_ids), ['id', 'datas_fname', 'name', 'file_type'], context=context)
+        attachments = ir_attachment_obj.read(cr, SUPERUSER_ID, list(attachment_ids), ['id', 'datas_fname', 'name', 'file_type_icon'], context=context)
         attachments_tree = dict((attachment['id'], {
             'id': attachment['id'],
             'filename': attachment['datas_fname'],
             'name': attachment['name'],
-            'file_type': attachment['file_type'],
+            'file_type_icon': attachment['file_type_icon'],
         }) for attachment in attachments)
 
         # 3. Update message dictionaries
diff --git a/addons/mail/static/src/xml/mail.xml b/addons/mail/static/src/xml/mail.xml
index 6ce588e82a2..28cbbca1f2c 100644
--- a/addons/mail/static/src/xml/mail.xml
+++ b/addons/mail/static/src/xml/mail.xml
@@ -88,10 +88,10 @@
         -->
     <t t-name="mail.thread.message.attachments">
         <t t-foreach='widget.attachment_ids' t-as='attachment'>
-            <t t-if="attachment.file_type !== 'webimage'">
+            <t t-if="attachment.file_type_icon !== 'webimage'">
                 <div t-attf-class="oe_attachment #{attachment.upload ? 'oe_uploading' : ''}">
                     <a t-att-href='attachment.url' target="_blank">
-                        <img t-att-src="'/mail/static/src/img/mimetypes/' + attachment.file_type + '.png'"></img>
+                        <img t-att-src="'/mail/static/src/img/mimetypes/' + attachment.file_type_icon + '.png'"></img>
                         <div class='oe_name'><t t-raw='attachment.name' /></div>
                     </a>
                     <div class='oe_delete oe_e' title="Delete this attachment" t-att-data-id="attachment.id">[</div>
@@ -100,7 +100,7 @@
                     </div>
                 </div>
             </t>
-            <t t-if="attachment.file_type === 'webimage'">
+            <t t-if="attachment.file_type_icon === 'webimage'">
                 <div t-attf-class="oe_attachment oe_preview #{attachment.upload ? 'oe_uploading' : ''}">
                     <a t-att-href='attachment.url' target="_blank">
                         <img t-att-src="widget.attachments_resize_image(attachment.id, [100,80])"></img>
diff --git a/addons/website_sale/views/website_sale.xml b/addons/website_sale/views/website_sale.xml
index 4f8a5404d74..a1b21137d94 100644
--- a/addons/website_sale/views/website_sale.xml
+++ b/addons/website_sale/views/website_sale.xml
@@ -419,11 +419,11 @@
                                 <div>
                                     <div class="oe_msg_attachment" t-foreach='message.attachment_ids' t-as='attachment'>
                                         <a t-att-href="'/mail/download_attachment?model=mail.message&amp;id='+str(message.id)+'&amp;method=download_attachment&amp;attachment_id='+str(attachment.id)" target="_blank">
-                                            <t t-if="attachment.file_type == 'webimage'">
+                                            <t t-if="attachment.file_type_icon == 'webimage'">
                                                 <img t-att-src="'/web/binary/image?model=ir.attachment&amp;field=datas&amp;id=' + str(attachment.id) + '&amp;resize=100,80'"
                                                     class='oe_attachment_embedded'></img>
                                             </t>
-                                            <t t-if="attachment.file_type != 'webimage'">
+                                            <t t-if="attachment.file_type_icon != 'webimage'">
                                                 <img t-att-src="'/mail/static/src/img/mimetypes/' + attachment.file_type + '.png'"
                                                     class='oe_attachment_webimage'></img>
                                             </t>