diff --git a/include/class_tests.inc b/include/class_tests.inc
index d944e11029765a9fe3206fef08be3406ecace32a..166242eab1994d4f62f3e8e0d9a5cb886edc4e07 100644
--- a/include/class_tests.inc
+++ b/include/class_tests.inc
@@ -49,7 +49,7 @@ class tests {
   /*! \brief Test if the given string contains characters allowed in a DNS name */
   public static function is_dns_name($str)
   {
-    return(preg_match("/^[a-z0-9\.\-_]*$/i",$str));
+    return(preg_match("/^[a-z0-9\.\-]*$/i",$str));
   }