Unexpected interval comparison

I came across an unexpected comparison (tested on PostgreSQL 9.4 and
9.6) for intervals with a large difference in magnitude.

I narrowed it down to this example, where comparisons with this range
give the wrong value:

postgres=# SELECT

'1 year'::interval > '3854933 years'::interval,

'1 year'::interval > '3854934 years'::interval,

'1 year'::interval > '32618664 years'::interval,

'1 year'::interval > '32618665 years'::interval;

?column? | ?column? | ?column? | ?column?

----------+----------+----------+----------

f | t | t | f

(1 row)

Is this a bug? Should I not be comparing intervals? It would seem the
interval type has enough information to give the correct answer here.

Regards,

Frazer McLean