Different result depending on order of joins

Hallo

I was a little surprised by this behavior.
Is this what is supposed to happen?

This query returns what I want:

with
a as (select generate_series(1,3) a_val)
,b as (select generate_series(1,2) b_val)
,c as (select generate_series(1,1) c_val)
select * from a
inner join c on a.a_val=c.c_val
full join b on a.a_val=b.b_val
;

I get all values from b since it only has a full join and nothing else.

But if I change the order in the joining like this:

with
a as (select generate_series(1,3) a_val)
,b as (select generate_series(1,2) b_val)
, c as (select generate_series(1,1) c_val)
select * from a
full join b on a.a_val=b.b_val
inner join c on a.a_val=c.c_val
;

also b is limited to only return value 1.

I thought that the join was defined by "on a.a_val=c.c_val"
and that the relation between b and the rest wasn't affected by that last inner join.

I use PostgreSQL 9.3.6

Is this the expected behavior?

Thanks

Nicklas Avén