diff --git a/src/Symfony/Component/Finder/Finder.php b/src/Symfony/Component/Finder/Finder.php
index 4d9b470fe1..2cdc3f51cd 100644
--- a/src/Symfony/Component/Finder/Finder.php
+++ b/src/Symfony/Component/Finder/Finder.php
@@ -407,6 +407,10 @@ class Finder implements \IteratorAggregate, \Countable
     /**
      * Excludes directories.
      *
+     * Directories passed as argument must be relative to the ones defined with the `in()` method. For example:
+     *
+     *     $finder->in(__DIR__)->exclude('ruby');
+     *
      * @param string|array $dirs A directory path or an array of directories
      *
      * @return $this