Updating LONG columns in 8.1.7

Hello all. I have a question about updating a LONG datatype
column in Oracle 8.1.7.

I have a STUDENT table like:

student_id                INTEGER PK
student_comments    LONG

I want to execute a command like this:

UPDATE student SET student_comments = student_comments || 'some new
comments' WHERE student_id = 1;

I am getting an error message indicating incompatible data types.
Do I have to do some sort of conversion/cast to add my new
comments to the existing ones ?

Thanks in advance