The "framework.trusted_proxies" configuration key has been removed in Symfony 3.3.

If you upgrade an existing Symfony application to the new 3.3.0 version, you may see this error (depending on your application configuration):

The solution¶

Remove the framework.trusted_proxies option from your config file and call the Request::setTrustedProxies() method in your front controller.

For example, if your original config was the following:

# app/config/config.yml framework : # ... trusted_proxies : [ 192.0.0.1 , 10.0.0.0/8 ]

Remove the trusted_proxies option entirely and add the following in the app.php file:

# web/app.php // BEFORE // ... $kernel = new AppKernel ( 'prod' , false ); Request :: setTrustedHeaderName ( Request :: HEADER_FORWARDED , null ); $request = Request :: createFromGlobals (); // ... // AFTER // ... $kernel = new AppKernel ( 'prod' , false ); Request :: setTrustedHeaderName ( Request :: HEADER_FORWARDED , null ); Request :: setTrustedProxies ([ '192.0.0.1' , '10.0.0.0/8' ]); $request = Request :: createFromGlobals (); // ...

You can do this change right now because it also works in Symfony versions prior to 3.3. That way you'll be ready to upgrade your application. When Symfony 3.3 is released, you can simplify the above using the new second argument of setTrustedProxies() method: