Why does replication need the old history file?

Hackers,

Sequence of events:

1. PITR backup of server on timeline 2.

2. Restored the backup to a new server, new-master.

3. Restored the backup to another new server, new-replica.

4. Started and promoted new-master (now on Timeline 3).

5. Started new-replica, connecting over streaming to new-master.

6. Get error message:

2015-06-11 12:24:14.503 PDT,,,7465,,5579e05e.1d29,1,,2015-06-11 12:24:14
PDT,,0,LOG,00000,"fetching timeline history file for timeline 2 from
primary server",,,,,,,,,""
2015-06-11 12:24:14.503 PDT,,,7465,,5579e05e.1d29,2,,2015-06-11 12:24:14
PDT,,0,FATAL,XX000,"could not receive timeline history file from the
primary server: ERROR: could not open file
""pg_xlog/00000002.history"": No such file or directory

Questions:

A. Why does the replica need 00000002.history? Shouldn't it only need
00000003.history?

B. Did something change in this regard in 9.3.6, 9.3.7 or 9.3.8? It was
working in our previous setup, on 9.3.5, although that could have just
been that the history file hadn't been removed from the backups yet.

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com