Segmentation fault: pg_upgrade 9.1 to 9.3: pg_dump: row number 0 is out of range 0..-1

Running a pg_upgrade task is causing Segmentation fault:

command: "/usr/lib/postgresql/9.3/bin/pg_dump" --host "/var/lib/postgresql"
--port 50432 --username "postgres" --schema-only --quote-all-identifiers
--binary-upgrade --format=custom --file="pg_upgrade_dump_6064585.custom"
"u" >> "pg_upgrade_dump_6064585.log" 2>&1
pg_dump: row number 0 is out of range 0..-1
Segmentation fault (core dumped)

Running this command:

/usr/lib/postgresql/9.3/bin/pg_upgrade \
-b /usr/lib/postgresql/9.1/bin \
-d /var/lib/postgresql/9.1/main \
-o "-c config_file=/etc/postgresql/9.1/main/postgresql.conf" \
-B /usr/lib/postgresql/9.3/bin \
-D /var/lib/postgresql/9.3/main \
-O "-c config_file=/etc/postgresql/9.3/main/postgresql.conf"

Any tips on how to diagnose and/or what might be the problem?

I've verified that the same extensions are present in 9.3 as exist in 9.1.
I'm not really sure how to proceed.

Performing Consistency Checks
-----------------------------
Checking cluster versions ok
Checking database user is a superuser ok
Checking for prepared transactions ok
Checking for reg* system OID user data types ok
Checking for contrib/isn with bigint-passing mismatch ok
Creating dump of global objects ok
Creating dump of database schemas

It then goes through about 3 or 4 databases and then faults.

gdb doesn't seem helpful:

$ gdb /usr/lib/postgresql/9.3/bin/pg_dump core
GNU gdb (GDB) 7.5-ubuntu
Reading symbols from /usr/lib/postgresql/9.3/bin/pg_dump...(no debugging
symbols found)...done.
[New LWP 1180]

warning: Can't read pathname for load map: Input/output error.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/usr/lib/postgresql/9.3/bin/pg_dump --host
/var/lib/postgresql --port 50432 --u'.
Program terminated with signal 11, Segmentation fault.
#0 0x00007fd05f7c2284 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0 0x00007fd05f7c2284 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007fd0601c1200 in ?? ()
#2 0x00007fd0601ca405 in ?? ()
#3 0x00007fd0601b5ffb in main ()

Thanks

Linux db 3.5.0-39-generic #60-Ubuntu SMP Tue Aug 13 18:33:05 UTC 2013
x86_64 x86_64 x86_64 GNU/Linux
Distributor ID: Ubuntu
Description: Ubuntu 12.10
Release: 12.10
Codename: quantal