diff --git a/admin_manual/installation/source_installation.rst b/admin_manual/installation/source_installation.rst
index ab2a9785f..45b57d2ea 100644
--- a/admin_manual/installation/source_installation.rst
+++ b/admin_manual/installation/source_installation.rst
@@ -126,6 +126,7 @@ Required:
 * PHP module XMLWriter
 * PHP module zip
 * PHP module zlib
+* PHP module session
 
 Database connectors (pick the one for your database:)