mySQL WHERE ... IN ( .. )

I’m trying to do a subquery using WHERE IN, but i can’t get mysql to recognize any Index. I’ve tried FORCE/USE INDEX(package) but it doesn’t use it

I have a simple index on package.
this is the EXPLAIN statement

FROM class_compjar
WHERE package
IN ( 1, 2, 3 )

id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE class_compjar ALL package NULL NULL NULL 23621 Using where