The issue first highlighted MONGOID-5813, which was closed as supposedly fixed with MONGOID-5819, is still present.
Using the minimal reproduction code I supplied in the first issue still raises the same error:
require "bundler/inline" gemfile do source "https://rubygems.org" # Include desired version when testing # gem "mongoid", "~> 8.0" gem "mongoid", "~> 9.0.3" end Mongoid.configure do |config| config.clients.default = { hosts: ["localhost:27017"], database: "foo", } end class Foo include Mongoid::Document store_in database: ->{ "foo" }, client: ->{ :bar } end puts "Mongoid: #{Mongoid::VERSION}" puts Foo.create # => undefined method `to_sym' for an instance of Proc (NoMethodError) name_as_symbol = name.to_sym