diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f077a15..e84065b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,6 +24,16 @@ jobs:
     - name: Check format
       run: nix-shell --run 'git ls-files | grep -P "\.py$" | xargs py2-astparse'
 
+  black-fmt:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: cachix/install-nix-action@v16
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - uses: actions/checkout@v2.4.0
+    - name: Check format
+      run: nix-shell --run 'black --check .'
+
   matrix_generate:
     runs-on: ubuntu-latest
     outputs: