diff --git a/security/access_control.rst b/security/access_control.rst
index 937944dd198..634f0b242aa 100644
--- a/security/access_control.rst
+++ b/security/access_control.rst
@@ -301,6 +301,15 @@ and functions including ``request``, which is the Symfony
 For a list of the other functions and variables, see
 :ref:`functions and variables <security-expression-variables>`.
 
+.. tip::
+
+    The ``allow_if`` expressions can also contain custom functions registered
+    with :ref:`expression providers <components-expression-language-provider>`.
+
+    .. versionadded:: 4.1
+        The feature to use custom functions inside ``allow_if`` expressions was
+        introduced in Symfony 4.1.
+
 Forcing a Channel (http, https)
 -------------------------------