diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 15391b8e56d..e8e2ffda124 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -19,16 +19,16 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
 
-      - uses: cachix/install-nix-action@v12
+      - uses: cachix/install-nix-action@07da2520eebede906fbeefa9dd0a2b635323909d # v12
         with:
           nix_path: nixpkgs=channel:nixos-20.09
           extra_nix_config: |
             trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
             substituters = https://hydra.iohk.io https://cache.nixos.org/
 
-      - uses: cachix/cachix-action@v8
+      - uses: cachix/cachix-action@6e4751ed42b22f60165d3f266cfa4cce66ae406d # v8
         with:
           name: amazonka
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}