diff --git a/plugins/plugin.php b/plugins/plugin.php
index 4535c1a4..35798c98 100644
--- a/plugins/plugin.php
+++ b/plugins/plugin.php
@@ -8,7 +8,7 @@
 class AdminerPlugin extends Adminer {
 	var $plugins;
 	
-	function _findRootClass($class) {
+	function _findRootClass($class) { // is_subclass_of(string, string) is available since PHP 5.0.3
 		do {
 			$return = $class;
 		} while ($class = get_parent_class($class));