data:migration giving strange error

I am trying to run this data migration.

class StateLabel < ActiveRecord::Migration
  def self.up

    states = {one: 'ONE', two: 'TWO', three: 'THREE'}

    Wms.all.each do |w|
      states.each do |k, v|
        StateLabel.create(wms_id: w.id, state: k.to_s, label: v)
      end
    end
  end

  def self.down
    raise IrreversibleMigration
  end
end

I'm getting this error:

== StateLabel: migrating ================================================ -- create({:wms_id=>1, :state=>"One", :label=>"ONE"}) rake aborted! An error has occurred, this and all later migrations canceled:

PG::SyntaxError: ERROR: syntax error at or near "{" LINE 1: {:wms_id=>1, :state=>"One", :label=>"ONE...

I can't see any syntax errors. I can run that code in the console just fine.

Any idea what's going on?