diff --git a/components/http_foundation/session_configuration.rst b/components/http_foundation/session_configuration.rst
index 33878afa906..66d0087189d 100644
--- a/components/http_foundation/session_configuration.rst
+++ b/components/http_foundation/session_configuration.rst
@@ -139,6 +139,20 @@ the ``php.ini`` directive ``session.gc_maxlifetime``. The meaning in this contex
 that any stored session that was saved more than ``gc_maxlifetime`` ago should be
 deleted. This allows one to expire records based on idle time.
 
+However, some operating systems do their own session handling and set the
+``session.gc_probability`` variable to ``0`` to stop PHP doing garbage
+collection. That's why Symfony now overwrites this value to ``1``.
+
+If you wish to use the original value set in your ``php.ini``, add the following
+configuration:
+
+.. code-block:: yaml
+
+    # config.yml
+    framework:
+        session:
+            gc_probability: null
+
 You can configure these settings by passing ``gc_probability``, ``gc_divisor``
 and ``gc_maxlifetime`` in an array to the constructor of
 :class:`Symfony\\Component\\HttpFoundation\\Session\\Storage\\NativeSessionStorage`