diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 1092c8d..4d8a937 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -9,6 +9,7 @@ jobs:
     strategy:
       matrix:
         tag:
+          - nixos-20.09
           - nixos-21.05
           - nixos-unstable
     runs-on: ubuntu-latest