Select subquery inside then of case when statement, sqlite bug?

I'm finding that when I try to select a column in a SQL case statement, it doesn't work unless I wrap it in a numeric function. The max(price) seems to select the value in the column, while just price, or price always returns blank.

I think its a bug.

This doesn't work:

SELECT 
auction,
CASE WHEN auction='1'
    THEN (select max(bid.amount) from bid where bid.auction_id = auction.id)
    ELSE price
END as price_string, 
FROM product 

This works:

SELECT 
auction,
CASE WHEN auction='1'
    THEN (select max(bid.amount) from bid where bid.auction_id = auction.id)
    ELSE max(price)
END as price_string 
FROM product