diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 20335c718..4b501e613 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -58,7 +58,7 @@ jobs:
 
   unit_tests:
     name: Unit tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     env:
       RUBY_YJIT_ENABLE: "1"
     services: