diff --git a/.github/workflows/periodics-daily.yaml b/.github/workflows/periodics-daily.yaml
index 468b79a..b276d1a 100644
--- a/.github/workflows/periodics-daily.yaml
+++ b/.github/workflows/periodics-daily.yaml
@@ -60,9 +60,9 @@ jobs:
     strategy:
       matrix:
         kubernetes:
-          - 1.18
-          - 1.19
-          - 1.20
+          - "1.18"
+          - "1.19"
+          - "1.20"
     steps:
       - uses: actions/checkout@v2
       - name: Find go version