migration error, mysql, change column limit

Hmm, one of my migrations have stopped working on #down. It still works on #up. (It's also possible that I never tested it for #down before, and it never worked, heh.)

I can't figure out why not. Pretty simple.

class WidenRequestParams < ActiveRecord::Migration   def self.up     change_column :requests, :params, :string, :limit => 2048   end

  def self.down     change_column :requests, :params, :string, :limit => 1024   end end

Up works fine. Down tells me:

Mysql::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'limit1024 DEFAULT NULL' at line 1: ALTER TABLE `requests` CHANGE `params` `params` limit1024 DEFAULT NULL

Why is it messing up the SQL on 'down', but not 'up'? Very weird. Anyone have any ideas?