diff --git a/lib/plugins/acl/ajax.php b/lib/plugins/acl/ajax.php
index d704fa8c9aa8bd53d7a8ecc2f7010a8a78d123f9..71a2eb03a1feaa75d074333b8da0e20040292a27 100644
--- a/lib/plugins/acl/ajax.php
+++ b/lib/plugins/acl/ajax.php
@@ -7,7 +7,7 @@
  */
 
 //fix for Opera XMLHttpRequests
-if(!count($_POST) && $HTTP_RAW_POST_DATA){
+if(!count($_POST) && !empty($HTTP_RAW_POST_DATA)){
   parse_str($HTTP_RAW_POST_DATA, $_POST);
 }