Need SELECT rights to UPDATE/DELETE WHERE?

PostgreSQL 8.0.0 on WinXP Pro, libpq

In my hands it looks like a user with INSERT/DELETE/UPDATE rights on table1
cannot do "update table1 set field1=xx where field2=yy" without also being
granted select rights. However, the user can do "update table1 set field1=xx".
Is this right? Any explanations why it should be like this and any suggestions
on how to get around it without granting select is greatly appreciated.

KP