Oracle - Subquery in IF Clause

I have the following code:

if USER IN (SELECT user_id from user_maint where roll = 12) THEN
        p_status := 'W';

ELSE 
        p_status := 'A';
END IF;

It gives the error: Error(332,16): PLS-00405: subquery not allowed in this context

How to make subquery in the IF clause?