diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index daad99e..b141a5c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -31,6 +31,7 @@ jobs:
           - ruby: 3.2
           - ruby: 3.3
           - ruby: 3.4
+          - ruby: "4.0"
           - ruby: head
             allow_failures: "allow failures"
 
diff --git a/README.md b/README.md
index 78bba7f..f1e3df4 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@ Really simple JSON and XML parsing, ripped from Merb and Rails. The XML parser i
 
 * Ruby 2.x
 * Ruby 3.x
+* Ruby 4.x
 
 ## note on patches/pull requests