Unknown key: :case_sensitive

[phlegx]

Rails: 4.1
DB: PostgreSQL 9.3
Adapter: Activerecord PostGis Adapter 2.2.1 https://github.com/rgeo/activerecord-postgis-adapter

In my database.yml I use this here (required adapter for PostGis):

development:
  adapter: postgis
  ...

My migration:

...
  def self.up
    change_table :users do |t|
      t.string :email, index: { case_sensitive: false, unique: true }
...

Any idea how to solve this problem?