What I'm I doing wrong?

through_polymorphic.rb

class User
  has_many :parameter_values, as: :valuable
  has_many :parameters,-> { uniq }, :through => :parameter_values
end

class ParameterValue
  belongs_to :parameter
  belongs_to :valuable, :polymorphic => true
end

class Parameter
  has_many :parameter_values
end

user = User.create()
paramater_value = ParameterValue.create(parameter_id: 6, valuable_id: 1, valuable_type: "User")
user.parameter_values << parameter_value

user.parameter_values # [#<ParameterValue id: 1, parameter_id: 6, valuable_id: 1, valuable_type: "User">]
user.parameters       # []  wtf?
user.parameters.explain # Last part of the query ["valuable_id", nil] should be ["valuable_id", 1]
=> EXPLAIN for: SELECT DISTINCT "parameters".* FROM "parameters" INNER JOIN "parameter_values" ON "parameters"."id" = "parameter_values"."parameter_id" WHERE "parameter_values"."valuable_id" = $1 AND "parameter_values"."valuable_type" = $2 [["valuable_id", nil], ["valuable_type", "User"]]