diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c7346a7..874f1f3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [2.6, 2.7, '3.0', 3.1, 3.2, ruby-head, jruby]
+        ruby: ['3.0', 3.1, 3.2, ruby-head, jruby]
     steps:
       - name: Clone repository
         uses: actions/checkout@v3
@@ -33,6 +33,6 @@ jobs:
         run: ruby --version; bundle exec rspec spec || $ALLOW_FAILURES
       - name: Coveralls GitHub Action
         uses: coverallsapp/github-action@v2
-        if: "matrix.ruby == '3.0'"
+        if: "matrix.ruby == '3.2'"
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/Gemfile b/Gemfile
index 035cdb7..37b84f8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,6 +16,6 @@ group :development do
 end
 
 group :development, :test do
-  gem 'simplecov', '~> 0.21',  platforms: :mri
+  gem 'simplecov', '~> 0.22',  platforms: :mri
   gem 'simplecov-lcov', '~> 0.8',  platforms: :mri
 end
diff --git a/README.md b/README.md
index 07e55f3..3b731c1 100644
--- a/README.md
+++ b/README.md
@@ -290,7 +290,7 @@ A copy of the [Turtle EBNF][] and derived parser files are included in the repos
 [ISO/IEC 14977]:https://www.iso.org/standard/26153.html
 [LL(1)]:        https://www.csd.uwo.ca/~moreno//CS447/Lectures/Syntax.html/node14.html
 [LL(1) Parser]: https://en.wikipedia.org/wiki/LL_parser
-[Logger]:       https://ruby-doc.org/stdlib-2.4.0/libdoc/logger/rdoc/Logger.html
+[Logger]:       https://ruby-doc.org/stdlib-3.0.0/libdoc/logger/rdoc/Logger.html
 [S-expression]: https://en.wikipedia.org/wiki/S-expression
 [Tokenizer]:    https://en.wikipedia.org/wiki/Lexical_analysis#Tokenizer
 [Turtle]:       https://www.w3.org/TR/2012/WD-turtle-20120710/
diff --git a/VERSION b/VERSION
index cc6c9a4..197c4d5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.5
+2.4.0
diff --git a/ebnf.gemspec b/ebnf.gemspec
index afdc9f1..930e201 100755
--- a/ebnf.gemspec
+++ b/ebnf.gemspec
@@ -28,17 +28,17 @@ Gem::Specification.new do |gem|
   gem.executables          = %w(ebnf)
   gem.require_paths         = %w(lib)
 
-  gem.required_ruby_version = '>= 2.6'
+  gem.required_ruby_version = '>= 3.0'
   gem.requirements          = []
   gem.add_runtime_dependency     'sxp',             '~> 1.2'
   gem.add_runtime_dependency     'scanf',           '~> 1.0'
-  gem.add_runtime_dependency     'rdf',             '~> 3.2' # Required by sxp
+  gem.add_runtime_dependency     'rdf',             '~> 3.3' # Required by sxp
   gem.add_runtime_dependency     'htmlentities',    '~> 4.3'
   gem.add_runtime_dependency     'unicode-types',   '~> 1.8'
   gem.add_development_dependency 'amazing_print',   '~> 1.4'
   gem.add_development_dependency 'rdf-spec',        '~> 3.2'
   gem.add_development_dependency 'rdf-turtle',      '~> 3.2'
-  gem.add_development_dependency 'nokogiri',        '~> 1.13', '>= 1.13.4'
+  gem.add_development_dependency 'nokogiri',        '~> 1.15', '>= 1.15.4'
   gem.add_development_dependency 'erubis',          '~> 2.7'
   gem.add_development_dependency 'rspec',           '~> 3.12'
   gem.add_development_dependency 'rspec-its',       '~> 1.3'