diff --git a/lib/russian_workdays/day.rb b/lib/russian_workdays/day.rb
index d98d716..7bc4d13 100644
--- a/lib/russian_workdays/day.rb
+++ b/lib/russian_workdays/day.rb
@@ -3,7 +3,10 @@
 require "yaml"
 
 module RussianWorkdays
-  DATES = YAML.load_file(File.join(__dir__, "dates.yml")).freeze
+  DATES = YAML.load_file(
+    File.join(__dir__, 'dates.yml'),
+    permitted_classes: [Date, Symbol]
+  ).freeze
 
   class Day
     def initialize(date)
diff --git a/russian_workdays.gemspec b/russian_workdays.gemspec
index 98dd350..0d5bcbc 100644
--- a/russian_workdays.gemspec
+++ b/russian_workdays.gemspec
@@ -18,6 +18,8 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
+  spec.required_ruby_version = '>= 2.6.3'
+
   spec.add_development_dependency "bundler", "~> 1.6"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"