Default order of select datname from pg_database

By any change, does the following query have an "order by" by default when omitted?:

select datname from pg_database;

I know you could pass and ORDER BY datname or similar but what I don't know is if by default there's some kind of sort when the order by is omitted.

I executed that query against one of my servers and while looking at the names it seems complety random, the order is always the same, for instance:

web2

template0

asdf

basic

postgres

web3

.....

Does anybody know?

Thanks in advance!
--