I am trying to do a CASE expression. The requirement is if Date field is NULL then show it as 'Pending' or else show the date from the db.

I have tried the below case expression but there is some problem.

CASE po_amend_received_date IS NULL WHEN 1 THEN 'Pending'  
ELSE po_amend_received_date END AS `po_amend_received_date`

What is my mistake?