diff --git a/addons/calendar/calendar_data.xml b/addons/calendar/calendar_data.xml
index ca8a951558c..b1ceb6cbd7c 100644
--- a/addons/calendar/calendar_data.xml
+++ b/addons/calendar/calendar_data.xml
@@ -125,7 +125,7 @@
             <field name="model_id" ref="calendar.model_calendar_attendee"/>
             
             <field name="email_to" >${('' if object.partner_id and object.partner_id.email and object.partner_id.email==object.email else object.email|safe)}</field>
-            <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and ("[%s]" % object.partner_id.id) or False }</field>
+            <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and object.partner_id.id or False }</field>
             <field name="auto_delete" eval="True"/>
             
             <field name="body_html"><![CDATA[
@@ -248,7 +248,7 @@
             <field name="model_id" ref="calendar.model_calendar_attendee"/>
             
             <field name="email_to" >${('' if object.partner_id and object.partner_id.email and object.partner_id.email==object.email else object.email|safe)}</field>
-            <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and ("[%s]" % object.partner_id.id) or False }</field>
+            <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and object.partner_id.id or False }</field>
             <field name="auto_delete" eval="True"/>
             
             <field name="body_html"><![CDATA[ 
@@ -373,7 +373,7 @@
             <field name="model_id" ref="calendar.model_calendar_attendee"/>
             
             <field name="email_to" >${('' if object.partner_id and object.partner_id.email and object.partner_id.email==object.email else object.email|safe)}</field>
-            <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and ("[%s]" % object.partner_id.id) or False }</field>
+            <field name="partner_to">${object.partner_id and object.partner_id.email and object.partner_id.email==object.email and object.partner_id.id or False }</field>
             <field name="auto_delete" eval="True"/>
             
             <field name="body_html"><![CDATA[