diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 67397ac..57dbc85 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest]
-        ruby-version: [2.3, 2.4, 2.5, 2.6, 2.7, 3.0]
+        ruby-version: ['2.3', '2.4', '2.5', '2.6', '2.7', '3.0', '3.1']
     steps:
       - uses: actions/checkout@v2