diff --git a/doctrine/custom_dql_functions.rst b/doctrine/custom_dql_functions.rst
index ee11967da47..974ee11987f 100644
--- a/doctrine/custom_dql_functions.rst
+++ b/doctrine/custom_dql_functions.rst
@@ -146,4 +146,8 @@ In Symfony, you can register your custom DQL functions as follows:
                 ],
             ]);
 
+.. caution::
+
+    It is not possible to inject Symfony services or parameters into a custom DQL function.
+
 .. _`DQL User Defined Functions`: https://www.doctrine-project.org/projects/doctrine-orm/en/current/cookbook/dql-user-defined-functions.html