diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f835e24..46ff062 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ['3.0', 3.1, 3.2, ruby-head, jruby]
+        ruby: ['3.0', 3.1, 3.2, 3.3, ruby-head, jruby]
     steps:
       - name: Clone repository
         uses: actions/checkout@v3
@@ -33,7 +33,7 @@ jobs:
         run: ruby --version; bundle exec rspec spec || $ALLOW_FAILURES
       - name: Coveralls GitHub Action
         uses: coverallsapp/github-action@v2
-        if: "matrix.ruby == '3.2'"
+        if: "matrix.ruby == '3.3'"
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
   wintests:
@@ -47,7 +47,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
-          - 3.1
+          - 3.2
     steps:
       - name: Clone repository
         uses: actions/checkout@v3
diff --git a/lib/yaml_ld.rb b/lib/yaml_ld.rb
index 894d707..bb865c5 100644
--- a/lib/yaml_ld.rb
+++ b/lib/yaml_ld.rb
@@ -13,7 +13,7 @@ module YAML_LD
   #   require 'yaml_ld'
   #
   # @example Parsing RDF statements from a YAML-LD file
-  #   JSON::LD::Reader.open("etc/foaf.YAML_LD") do |reader|
+  #   JSON::LD::Reader.open("etc/foaf.yamlld") do |reader|
   #     reader.each_statement do |statement|
   #       puts statement.inspect
   #     end
diff --git a/lib/yaml_ld/format.rb b/lib/yaml_ld/format.rb
index c2fd478..33c01fd 100644
--- a/lib/yaml_ld/format.rb
+++ b/lib/yaml_ld/format.rb
@@ -7,17 +7,17 @@ module YAML_LD
   # YAML-LD format specification.
   #
   # @example Obtaining an YAML-LD format class
-  #     RDF::Format.for(:YAML_LD)           #=> YAML_LD::Format
-  #     RDF::Format.for("etc/foaf.YAML_LD")
-  #     RDF::Format.for(:file_name         => "etc/foaf.YAML_LD")
-  #     RDF::Format.for(file_extension: "YAML_LD")
+  #     RDF::Format.for(:yamlld)           #=> YAML_LD::Format
+  #     RDF::Format.for("etc/foaf.yamlld")
+  #     RDF::Format.for(:file_name         => "etc/foaf.yamlld")
+  #     RDF::Format.for(file_extension: "yamlld")
   #     RDF::Format.for(:content_type   => "application/ld+yaml")
   #
   # @example Obtaining serialization format MIME types
   #     RDF::Format.content_types      #=> {"application/ld+yaml" => [YAML_LD::Format],
   #
   # @example Obtaining serialization format file extension mappings
-  #     RDF::Format.file_extensions    #=> {:YAML_LD => [YAML_LD::Format] }
+  #     RDF::Format.file_extensions    #=> {:yamlld => [YAML_LD::Format] }
   #
   # @see https://json-ld.github.io/yaml-ld/spec/
   # @see https://json-ld.github.io/yaml/tests/
diff --git a/yaml-ld.gemspec b/yaml-ld.gemspec
index bf23ea7..03027da 100755
--- a/yaml-ld.gemspec
+++ b/yaml-ld.gemspec
@@ -33,6 +33,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency     'psych',           '>= 3.3' # Rails 6.0 cannot use psych 4.0
   gem.add_runtime_dependency     'rdf',             '~> 3.3'
   gem.add_runtime_dependency     'rdf-xsd',         '~> 3.3'
+  gem.add_development_dependency 'getoptlong',      '~> 0.2'
   gem.add_development_dependency 'rdf-isomorphic',  '~> 3.3'
   gem.add_development_dependency 'rdf-spec',        '~> 3.3'
   gem.add_development_dependency 'rdf-trig',        '~> 3.3'