unknown type name ‘pg_int64’

I am getting the error following errors trying to install pg_repack via
pgxn on Ubuntu server 12.04.4 with all PostgreSQL packages from pgdg:

gcc -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat
-Wformat-security -Werror=format-security -fPIC -pie
-fno-omit-frame-pointer -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels -Wformat-security
-fno-strict-aliasing -fwrapv -fexcess-precision=standard -g
-I/usr/include/postgresql -DREPACK_VERSION=1.2.1 -I. -I./
-I/usr/include/postgresql/9.1/server -I/usr/include/postgresql/internal
-D_FORTIFY_SOURCE=2 -DLINUX_OOM_ADJ=0 -D_GNU_SOURCE
-I/usr/include/libxml2 -I/usr/include/tcl8.5 -c -o pg_repack.o pg_repack.c
In file included from pgut/pgut.h:21:0,
from pgut/pgut-fe.h:13,
from pg_repack.c:25:
/usr/include/postgresql/libpq-fe.h:547:1: error: unknown type name
‘pg_int64’
/usr/include/postgresql/libpq-fe.h:547:50: error: unknown type name
‘pg_int64’
/usr/include/postgresql/libpq-fe.h:551:1: error: unknown type name
‘pg_int64’
/usr/include/postgresql/libpq-fe.h:553:48: error: unknown type name
‘pg_int64’

I found mention of a similar issue relating to repmgr reported by Josh
Berkus here but no recommended solution:
https://groups.google.com/forum/#!topic/repmgr/0rSwzVFlPsM

On that thread someone requested the output of "dpkg -l | grep postgres"
so I'll preemptively post it here:
ii pgdg-keyring 2013.2 keyring for
apt.postgresql.org
ii postgresql-9.1 9.1.13-1.pgdg12.4+1 object-relational
SQL database, version 9.1 server
ii postgresql-client-9.1 9.1.13-1.pgdg12.4+1 front-end
programs for PostgreSQL 9.1
ii postgresql-client-common 154.pgdg12.4+1 manager
for multiple PostgreSQL client versions
ii postgresql-common 154.pgdg12.4+1 PostgreSQL
database-cluster manager
ii postgresql-contrib-9.1 9.1.13-1.pgdg12.4+1 additional
facilities for PostgreSQL
ii postgresql-doc-9.1 9.1.13-1.pgdg12.4+1 documentation
for the PostgreSQL database management system
ii postgresql-server-dev-9.1 9.1.13-1.pgdg12.4+1
development files for PostgreSQL 9.1 server-side programming

Cheers,
Steve