diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index eabe029..8d2602c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -17,13 +17,17 @@ jobs:
 
       - name: Install Nix
         uses: cachix/install-nix-action@c134e4c9e34bac6cab09cf239815f9339aaaf84e # v31.5.1
-
       - name: Use Cachix Cache
         uses: cachix/cachix-action@3ba601ff5bbb07c7220846facfa2cd81eeee15a1 # v16
         with:
           name: nxpg
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
 
+      - name: Check flake.lock/flake.nix for drift
+        run: |
+          nix flake update
+          git diff --exit-code
+
       - name: Build
         run: nix-shell --argstr pgVersion "${{ matrix.pg-version }}" --arg cassert true --run "xpg -v ${{ matrix.pg-version }} build"