I'm using options exactly per docs, at http://mongoid.org/en/mongoid/docs/installation.html

options:
read: :secondary
write:
w: :majority

Error is:

/Volumes/Data/Apps/sardel/shared/bundle/ruby/2.2.0/gems/optionable-0.2.0/lib/optionable/validator.rb:50:in `validate!':

{"w"=>:majority}

is not acceptable for option :write. Valid values are: {:w=>any Integer},

{"w"=>any Integer}

, {:w=>any String},

{"w"=>any String}

, {:j=>true},

{"j"=>true}

, {:j=>false},

{"j"=>false}

, {:fsync=>true},

{"fsync"=>true}

, {:fsync=>false},

{"fsync"=>false}

. (Optionable::Invalid)

Workaround: using a string (majority) rather than a symbol (:majority)