diff --git a/components/filesystem.rst b/components/filesystem.rst
index 1ab82a96035..17188aa9c33 100644
--- a/components/filesystem.rst
+++ b/components/filesystem.rst
@@ -68,6 +68,13 @@ On POSIX filesystems, directories are created with a default mode value
 
     This function ignores already existing directories.
 
+.. note::
+
+    The directory permissions are affected by the current `umask`_.
+    Set the umask for your webserver, use PHP's :phpfunction:`umask`
+    function or use the :phpfunction:`chmod` function after the
+    directory has been created.
+
 exists
 ~~~~~~
 
@@ -278,3 +285,4 @@ Learn More
     filesystem/*
 
 .. _`Packagist`: https://packagist.org/packages/symfony/filesystem
+.. _`umask`: https://en.wikipedia.org/wiki/Umask