diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a1ce7996..4e27ae76 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -25,6 +25,7 @@ jobs:
           - "3.2"
           - "3.3"
           - "3.4"
+          - "4.0"
           - "jruby-9.4"
           - "truffleruby"
     steps:
diff --git a/docker-compose.yml b/docker-compose.yml
index 4fbfbec8..d570d43b 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -92,6 +92,20 @@ services:
       - .:/code
     working_dir: /code
 
+  ci-4.0:
+    image: ruby:4.0
+    entrypoint: /code/ci-run.sh
+    environment:
+      INTEGRATION: openldap
+      INTEGRATION_HOST: ldap.example.org
+    depends_on:
+      - openldap
+    networks:
+      integration_test_network:
+    volumes:
+      - .:/code
+    working_dir: /code
+
   # https://github.com/flavorjones/truffleruby/pkgs/container/truffleruby
   ci-truffleruby:
     image: ghcr.io/flavorjones/truffleruby:stable
diff --git a/test/integration/test_bind.rb b/test/integration/test_bind.rb
index 4a1a0194..79304d29 100644
--- a/test/integration/test_bind.rb
+++ b/test/integration/test_bind.rb
@@ -16,7 +16,7 @@ def test_bind_timeout
     end
     msgs = ['Operation timed out - user specified timeout',
             'Connection timed out - user specified timeout']
-    assert_send([msgs, :include?, error.message])
+    assert msgs.any? { |m| error.message.include?(m) }, "unexpected message: #{error.message.inspect}"
   end
 
   def test_bind_anonymous_fail