diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index b0683b1..68590f1 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -27,7 +27,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: cachix/install-nix-action@v13
         with:
-          nix_path: nixpkgs=channel:nixos-unstable
+          nix_path: nixpkgs=channel:nixos-20.09
       - run: "nix-shell --run 'nanoc --env=prod'"
       - uses: actions/checkout@v2