diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1f8ef83..7f30608 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -202,7 +202,7 @@ jobs:
 
   testFixedBundlerVersionForOldRuby:
     name: "Test bundler: 1.x for old Ruby"
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v3
       - uses: ./