Name [comp/env] is not bound in this Context. Unable to find [comp] on JBossEWS on Openshift

I am using context in Java web application deployed on Tomcat (JBossEWS) on Openshift.

I look it up like this:

 Context context = new InitialContext();
 Context envContext = (Context) context.lookup("java:comp/env");

This works on my local Tomcat 7 but I get

javax.naming.NameNotFoundException: Name [comp/env] is not bound in this Context. Unable to find [comp].

when it is deployed to Openshift. I thought that comp/env is available by default.

Do I need to initialize it somehow?

How can I make it work?