space reserved for WAL record does not match what was written: panic on windows

In HEAD of 9.4 I'm getting the following:

D:\9.4\bin>postgres.exe -D d:\9.4\data
LOG: database system was shut down at 2013-10-05 00:43:33 NZDT
LOG: database system is ready to accept connections
LOG: autovacuum launcher started
PANIC: space reserved for WAL record does not match what was written:
CurrPos = 18446744071562067968 EndPos = 2147483648
STATEMENT: insert into test (items) select x.x from
generate_series(1,10000000) x(x);
LOG: server process (PID 5476) exited with exit code 3
DETAIL: Failed process was running: insert into test (items) select x.x
from generate_series(1,10000000) x(x);
LOG: terminating any other active server processes

debug_assertions = on

I made a slight change to the line that causes the panic to print out the
values of CurrPos and EndPos, as you can see above.

Only changes made to postgresql.conf are:

checkpoint_segments = 64 # in logfile segments, min 1, 16MB each
checkpoint_timeout = 15min # range 30s-1h

I discovered this was happening just after I bumped the checkpoint segment
up to 64 for bulk loading some test data.

create table test (
id serial not null,
name varchar(64) not null default 'name of something',
price numeric(10,2) not null default 1000.00,
active boolean not null default true,
items int not null default 1,
description text not null default 'description of item',
primary key(id)
);

insert into test (items) select x.x from generate_series(1,10000000) x(x);

I'm running this on windows 7 64bit with postgres compiled as 32bit.

Regards

David