Amazon web services – In AWS redshift, the json_extract_path_text function return empty string instead NU

In AWS Redshift, I am using json_extract_path_text function to parse simple Json.
I deliberately try to find non exists element in the Json so the function should return NULL.
If I use the function in ‘standalone’ select, the function return NULL as expected but if the function is used in select from table then a string empty ("") returned.
Here a simple example:

select json_extract_path_text('{"A":"B"}', 'AA'); --> Return NULL as expected.

create table #test (
    payload varchar(max)
);
insert into #test (payload) values ('{"A":"B"}');

select json_extract_path_text(payload,'AA') from #test; --> Return empty string

How can I make the function return null from select table query?
Thanks.

I try everything…