diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 316c151..6c1b14f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        ruby-version: ['2.4, '2.5', '2.6', '2.7', '3.0']
+        ruby-version: ['2.4', '2.5', '2.6', '2.7', '3.0']
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout repository