diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ff16c51..ab863b6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php: [7.4, 8.0]
+        php: ['7.4', '8.0']
     steps:
     - uses: actions/checkout@v1
     - name: Install dependencies