SQLLite case query

Hi

How do you tell SQLLite to not change what's in the row if none of the case conditions are met?

'UPDATE table SET tag1=' +

                    'CASE ' +

                    'WHEN tag1="Blah" THEN "Blah new" ' +

                    'WHEN tag1="Blah2" THEN "Blah2 new" ' +

                    'ELSE tag1=tag1 ' +

                    'END';// +

'ELSE tag1=tag1 ' inserts the number 1 into all ELSE columns, and leaving that line out altogether empties whatevers in that column.

Cheers guys