PostgreSQL Inconsistent Lexicographic Sort

gistfile1.txt

Run this SQL:

CREATE TEMPORARY TABLE SORTER ( name VARCHAR ); 
INSERT INTO SORTER (name) VALUES ('A B'); 
INSERT INTO SORTER (name) VALUES ('AB'); 
INSERT INTO SORTER (name) VALUES ('A C'); 
INSERT INTO SORTER (name) VALUES ('AC'); 

SELECT * FROM SORTER ORDER BY name; 
SELECT * FROM SORTER ORDER BY name DESC;

On OSX PostgreSQL 9.4.1:

 name
------
 A B
 A C
 AB
 AC
(4 rows)

 name
------
 AC
 AB
 A C
 A B
(4 rows)


On Linux PostgreSQL 9.4.4:

 name
------
 AB
 A B
 AC
 A C
(4 rows)

 name
------
 A C
 AC
 A B
 AB
(4 rows)

On Linux PostgreSQL 9.3.11, results are like OS X.

Locale is always en_US.UTF-8.

Confirmed with 9.5.0 on both and client_encoding=SQL_ASCII

I suspect this is due to an underlying library difference, although the OS level sort command seems to do the same thing on both platform.