Openfire 4.0.2 problem

Hello,

after upgrade to 4.0.2 I'm unable to log in to the server. The log shows something like this:

2016.03.24 13:05:13 WARN  [socket_c2s_ssl-thread-3]: org.jivesoftware.openfire.nio.ConnectionHandler - Closing connection due to exception in session: (0x00000002: nio socket, server, /192.168.0.8:52157 => /89.233.179.14:5223)

java.lang.NoSuchMethodError: java.util.concurrent.ConcurrentHashMap.keySet()Ljava/util/concurrent/Concurrent HashMap$KeySetView;

What's the problem?