invalid memory alloc request size on simple query with array_agg on Postgres 9.3

Postgresql 9.3 - Debian 7 54gb RAM 8 cores (On google compute engine)

I have a huge table called search_token (~50M rows) and I'm trying to execute a very simple query that is:

select array_agg(st.search_token) from search_token st limit 200

This column search_token is a varchar(25) and I'm getting this error:

ERROR:  invalid memory alloc request size 1073741824

If I remove the array_agg from the query, it runs smoothly in 1ms.

It used to work fine and started to fail on last days. Nothing was changed in the config file or on OS config.