Strange interval arithmetic

What's going on here?  Some sort of integer wraparound?

WORKS
=====

mysql=# select interval '2378 seconds'; interval
---------- 00:39:38
(1 row)

mysql=#
mysql=# select 2378 * interval '1 second'; ?column?
---------- 00:39:38
(1 row)

DOESN'T WORK
============

test=# select interval '2378234234 seconds';   interval
-------------- 596523:14:07
(1 row)

test=# select 2378234234 * interval '1 second';   ?column?
-------------- 660620:37:14
(1 row)