diff --git a/addressbook/inc/class.bocontacts.inc.php b/addressbook/inc/class.bocontacts.inc.php
index 4d58e560bd..c8e5acabae 100755
--- a/addressbook/inc/class.bocontacts.inc.php
+++ b/addressbook/inc/class.bocontacts.inc.php
@@ -420,9 +420,10 @@ class bocontacts extends socontacts
 	*
 	* @param mixed &$contact contact array with key id or (array of) id(s)
 	* @param boolean $deny_account_delete=true if true never allow to delete accounts
-	* @return boolean true on success or false on failiure
+	* @param int $check_etag=null
+	* @return boolean|int true on success or false on failiure, 0 if etag does not match
 	*/
-	function delete($contact,$deny_account_delete=true)
+	function delete($contact,$deny_account_delete=true,$check_etag=null)
 	{
 		if (is_array($contact) && isset($contact['id']))
 		{
@@ -436,14 +437,15 @@ class bocontacts extends socontacts
 		{
 			$id = is_array($c) ? $c['id'] : $c;
 
-			if ($this->check_perms(EGW_ACL_DELETE,$c,$deny_account_delete) && parent::delete($id))
+			$ok = false;
+			if ($this->check_perms(EGW_ACL_DELETE,$c,$deny_account_delete) && ($ok = parent::delete($id,$check_etag)))
 			{
 				egw_link::unlink(0,'addressbook',$id);
 				$GLOBALS['egw']->contenthistory->updateTimeStamp('contacts', $id, 'delete', time());
 			}
 			else
 			{
-				return false;
+				return $ok;
 			}
 		}
 		return true;
diff --git a/addressbook/inc/class.socontacts.inc.php b/addressbook/inc/class.socontacts.inc.php
index ed56e78161..624f94edb8 100755
--- a/addressbook/inc/class.socontacts.inc.php
+++ b/addressbook/inc/class.socontacts.inc.php
@@ -403,14 +403,18 @@ class socontacts
 	* deletes contact entry including custom fields
 	*
 	* @param mixed $contact array with id or just the id
-	* @return boolean true on success or false on failiure
+	* @param int $check_etag=null
+	* @return boolean|int true on success or false on failiure, 0 if etag does not match
 	*/
-	function delete($contact)
+	function delete($contact,$check_etag=null)
 	{
 		if (is_array($contact)) $contact = $contact['id'];
 
+		$where = array('id' => $contact);
+		if ($check_etag) $where['etag'] = $check_etag;
+
 		// delete mainfields
-		if ($this->somain->delete($contact))
+		if ($this->somain->delete($where))
 		{
 			// delete customfields, can return 0 if there are no customfields
 			$this->soextra->delete(array($this->extra_id => $contact));
@@ -430,7 +434,7 @@ class socontacts
 			}
 			return true;
 		}
-		return false;
+		return $check_etag ? 0 : false;		// if etag given, we return 0 on failure, thought it could also mean the whole contact does not exist
 	}
 
 	/**