diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 3d69c325..6e989198 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -34,6 +34,10 @@ jobs:
             fuzz: -DFMT_FUZZ=ON -DFMT_FUZZ_LINKMAIN=ON
             std: 17
             os: ubuntu-18.04
+          - cxx: clang++-11
+            build_type: Debug
+            std: 20
+            os: ubuntu-20.04
 
     steps:
     - uses: actions/checkout@v2