diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 9f91e34..8e89a8b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -22,7 +22,8 @@ jobs:
           '3.2',
           '3.3',
           '3.4',
-          'head'
+          'head',
+          'truffleruby-head'
           ]
         ruby-opt: [""]
         include:
diff --git a/test/test_auth.rb b/test/test_auth.rb
index 95c1718..0606ae7 100644
--- a/test/test_auth.rb
+++ b/test/test_auth.rb
@@ -227,6 +227,8 @@ def test_BASIC_auth_nil_uri
   #   Util.uri_part_of(target_uri, uri) and ok
   # }
   def test_BASIC_auth_multi_thread
+    omit "Fails on TruffleRuby" if RUBY_ENGINE == "truffleruby"
+
     c = HTTPClient.new
     webrick_backup = @basic_auth.instance_eval { @auth_scheme }
     begin