Postgres function returning wrong datatype

I am trying to install ubuntuone on a ubuntu server 15.04 and it seems there are a few things that aren't working anymore.

The main problem I have is a query that is failing. Here is how it looks like:

CREATE FUNCTION activity() RETURNS SETOF pg_stat_activity
    LANGUAGE sql SECURITY DEFINER
    SET search_path TO public
    AS $$
    SELECT
        datid, datname, pid, usesysid, usename,
        application_name, client_addr, client_hostname, client_port,
        backend_start, xact_start, query_start, waiting,
        CASE
            WHEN query LIKE '<IDLE>%'
                OR query LIKE 'autovacuum:%'
                THEN query
            ELSE
                '<HIDDEN>'
        END AS current_query
    FROM pg_catalog.pg_stat_activity;
$$;

When I run it I get this error:

ERROR:  return type mismatch in function declared to return pg_stat_activity
DETAIL:  Final statement returns boolean instead of timestamp with time zone at column 13.
CONTEXT:  SQL function "activity"

I understand the error, but I don't know how it is returning a bool. I ran the same query manually and still get the same error. Note that I am not too familiar with postgres so please be detailed.

What part of the query is returning a bool? or is the query correct at all?

Note the application was written for postgresql-9.1 but I am ruing 9.4