diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 707916ea2..9bc7fbbfe 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-13]
+        os: [ubuntu-20.04, macos-13]
         toolchain:
           - {compiler: gcc, version: 10}
           - {compiler: gcc, version: 11}