RAISE EXCEPTION not working

I am trying the use the following statements in a function:
SELECT INTO temp_i id FROM public.t_customer_profile WHERE
id=cust_id;
IF NOT FOUND THEN
RAISE EXCEPTION "Username already exists";
END IF;

I know the table and the select statement is correct.
And I keep receiving the following error:
WARNING: plpgsql: ERROR during compile of f_insert_login_profile_record
near line 19

ERROR: syntax error at or near ""Username already exists""

I do not understand why.

Thank you.
Brian H Mayo
<mailto:bmayo(at)comcast(dot)net> bmayo(at)comcast(dot)net