version mismatch detection doesn't work

Hackers,

Seems the functionality to detect old versions of the postmaster with
newer psql doesn't work.  Here, server is 7.2.1:

$ psql alvherre
ERROR:  parser: parse error at or near "."
Welcome to psql 7.3b1, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms      \h for help with SQL commands      \? for help on internal slash commands
    \g or terminate with semicolon to execute query      \q to quit
 

alvherre=> select version();                          version                           
-------------------------------------------------------------PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC
2.96
(1 row)

alvherre=> 

-- 
Alvaro Herrera (<alvherre[a]atentus.com>)
"Nunca confiaré en un traidor.  Ni siquiera si el traidor lo he creado yo"
(Barón Vladimir Harkonnen)