diff --git a/phpBB/phpbb/extension/finder.php b/phpBB/phpbb/extension/finder.php
index d3e73bc387..ffcb2c830e 100644
--- a/phpBB/phpbb/extension/finder.php
+++ b/phpBB/phpbb/extension/finder.php
@@ -286,7 +286,7 @@ class finder
 			else
             {
                 $class = preg_replace('#^ext/#', '', $class);
-				$classes[] = str_replace('/', '\\', $class);
+				$classes[] = '\\' . str_replace('/', '\\', $class);
 			}
 		}
 		return $classes;