diff --git a/PHPUnit/Util/GlobalState.php b/PHPUnit/Util/GlobalState.php
index 7f10096de90..8d89b51c78c 100644
--- a/PHPUnit/Util/GlobalState.php
+++ b/PHPUnit/Util/GlobalState.php
@@ -406,7 +406,7 @@ public static function phpunitFiles()
      */
     protected static function addDirectoryContainingClassToPHPUnitFilesList($className, $parent = 1)
     {
-        if (!class_exists($className)) {
+        if (!class_exists($className, false)) {
             return;
         }