Error on slave2 after promoting slave1 to master in cascaded streaming replication

I've a setup like MASTER -> SLAVE1 -> SLAVE2. MASTER and SLAVE2 are running on different ports on single server. SLAVE1 in on another server.

For testing purpose I've powered off my first server which holds MASTER and SLAVE1 databases and then promote SLAVE1 to master. When the server was turned on and slave2 was started, I am getting following errors in slave2 logs:

LOG:  restarted WAL streaming at 0/13000000 on timeline 4
LOG:  replication terminated by primary server
DETAIL:  End of WAL reached on timeline 4 at 0/13008B38.

Any idea how to address this issue and continue slave2 replicating from slave1 which is now promoted to MASTER?

Thanks