diff --git a/configuration/environment_variables.rst b/configuration/environment_variables.rst
index 50a2bd77daf..8ea248cac30 100644
--- a/configuration/environment_variables.rst
+++ b/configuration/environment_variables.rst
@@ -77,7 +77,7 @@ whenever the corresponding environment variable is *not* found:
 
         # config/services.yaml
         parameters:
-            env(DATABASE_HOST): localhost
+            env(DATABASE_HOST): 'localhost'
 
     .. code-block:: xml
 
@@ -97,6 +97,12 @@ whenever the corresponding environment variable is *not* found:
         // config/services.php
         $container->setParameter('env(DATABASE_HOST)', 'localhost');
 
+.. deprecated:: 4.3
+
+    Passing non-string values as default values for environment variables is
+    deprecated since Symfony 4.3. Use :ref:`environment variable processors <env-var-processors>`
+    if you need to transform those string default values into other data types.
+
 .. _configuration-env-var-in-prod:
 
 Configuring Environment Variables in Production
@@ -132,6 +138,8 @@ the following:
     :doc:`Symfony profiler </profiler>`. In practice this shouldn't be a
     problem because the web profiler must **never** be enabled in production.
 
+.. _env-var-processors:
+
 Environment Variable Processors
 -------------------------------