ALTER TABLE ADD field getting ORA-00942 error

I run the following command:

ALTER TABLE users
ADD date_terminated DATE DEFAULT SYSDATE NULL;
Commit;

and I get the following error message:

SQL Error: ORA-00942: table or view does not exist 00942. 00000 – “table or view does not exist”

*Cause:
*Action:

When I select * from users, I get records. Can someone tell me what I am doing wrong here?

Answer

This was a permissions issue: I did not use the owner of the table to alter the table. Switching to a connection with those credentials fixed the issue.