diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 61ad202..5b91601 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,7 +14,7 @@ jobs:
       with:
         nix_path: nixpkgs=channel:nixos-unstable
         extra_nix_config: experimental-features = nix-command
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2.4.0
     - name: Check format
       run: ./check-fmt
 
@@ -29,7 +29,7 @@ jobs:
       with:
         nix_path: nixpkgs=channel:nixos-unstable
         extra_nix_config: experimental-features = nix-command
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2.4.0
     - uses: cachix/cachix-action@v10
       with:
         name: poetry2nix