Sequel issue

gistfile1.rb

Sequel.migration do
  change do
    create_table :reports do
      primary_key :id

      column :name, String, null: false
      column :product, String, null: false
      column :category, String
      column :topics, 'varchar[]'
      column :expired_at, Time
      column :updated_at, Time, null: false
      column :created_at, Time, null: false

      foreign_key :question_id, :questions, null: false

      index :question_id
    end
  end
end

gistfile2.txt

[12] pry(main)> a = Report.new({name: 'n', product: 'p', question_id: '123'})
=> #<Report @values={:name=>"n", :product=>"p", :question_id=>123, :topics=>[]}>
[13] pry(main)> a.valid?
E,2014-03-13 12:24:35: PG::UndefinedFunction: ERROR:  operator does not exist: character varying[] = text[]
LINE 1: ..."name" = 'n') AND ("product" = 'p') AND ("topics" = ARRAY[]:...
                                                             ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.: SELECT count(*) AS "count" FROM "reports" WHERE (("name" = 'n') AND ("product" = 'p') AND ("topics" = ARRAY[]::text[])) LIMIT 1
Sequel::DatabaseError: PG::UndefinedFunction: ERROR:  operator does not exist: character varying[] = text[]
LINE 1: ..."name" = 'n') AND ("product" = 'p') AND ("topics" = ARRAY[]:...
                                                             ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
from /Users/rmartin/Development/peer60/reaction/vendor/bundle/gems/sequel-4.1.1/lib/sequel/adapters/postgres.rb:161:in `exec'