diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e930696..9ab3699 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,5 +1,8 @@
 name: CI
 
+env:
+  RUBYOPT: --enable=frozen-string-literal --debug=frozen-string-literal
+
 on:
   push:
     branches:
@@ -23,7 +26,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.7", "3.0", "3.1", "3.2", "3.3", ruby-head, jruby-9.4]
+        ruby: ["2.7", "3.0", "3.1", "3.2", "3.3", "3.4.0-preview2", ruby-head, jruby-9.4]
         rubocop_version: ["1.48", "1.66"]
     env:
       BUNDLE_GEMFILE: "gemfiles/rubocop_${{ matrix.rubocop_version }}.gemfile"