change column datatype in sql

hi

I have table in database that has Id column and it is int  primary key 

now I want change id column datatype to BIGINT I wrote below query:

alter table House_classification
alter column id bigint

but below error happen

Msg 5074, Level 16, State 1, Line 1The object 'PK_House_classification' is dependent on column 'id'.Msg 4922, Level 16, State 9, Line 1ALTER TABLE ALTER COLUMN id failed because one or more objects access this column.

what should I do?

Best regards

Neda