diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index 1d00469..16c65f8 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['2.7']
+        ruby-version: ['2.7', '3.3']
 
     steps:
     - uses: actions/checkout@v2
diff --git a/lib/readability.rb b/lib/readability.rb
index 4e4309f..2279517 100644
--- a/lib/readability.rb
+++ b/lib/readability.rb
@@ -43,7 +43,7 @@ def initialize(input, options = {})
       @options = DEFAULT_OPTIONS.merge(options)
       @input = input
 
-      if RUBY_VERSION =~ /^(1\.9|2)/ && !@options[:encoding]
+      if RUBY_VERSION =~ /^(1\.9|2|3)/ && !@options[:encoding]
         @input = GuessHtmlEncoding.encode(@input, @options[:html_headers]) unless @options[:do_not_guess_encoding]
         @options[:encoding] = @input.encoding.to_s
       end