After upgrading Jenkins from 1.551 to 1.552, the Manage Jenkins screen has the message "It appears that your reverse proxy set up is broken." The reverse proxy configuration has been correctly working before the upgrade.

The test URI
/jenkins/administrativeMonitor/hudson.diagnosis.ReverseProxySetupMonitor/test
is redirecting to
/jenkins/administrativeMonitor/hudson.diagnosis.ReverseProxySetupMonitor/testForReverseProxySetup/a%2Fb/
which is giving a 404 error.

In previous versions of Jenkins, it redirected to
/jenkins/administrativeMonitor/hudson.diagnosis.ReverseProxySetupMonitor/test-for-reverse-proxy-setup
which returned 200 OK.

I am using Apache Web Server with mod_proxy_ajp as a reverse proxy in front of the Tomcat serving Jenkins.