diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 874f1f3..473bc09 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
@@ -33,6 +33,6 @@ jobs:
         run: ruby --version; bundle exec rspec spec || $ALLOW_FAILURES
       - name: Coveralls GitHub Action
         uses: coverallsapp/github-action@v2
-        if: "matrix.ruby == '3.2'"
+        if: "matrix.ruby == '3.3'"
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/ebnf.gemspec b/ebnf.gemspec
index 049d7e5..2dabea7 100755
--- a/ebnf.gemspec
+++ b/ebnf.gemspec
@@ -35,6 +35,7 @@ Gem::Specification.new do |gem|
   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_runtime_dependency     'base64',      '~> 0.2'
   gem.add_development_dependency 'amazing_print',   '~> 1.4'
   gem.add_development_dependency 'rdf-spec',        '~> 3.3'
   gem.add_development_dependency 'rdf-turtle',      '~> 3.3'