diff --git a/.github/workflows/foundry.yml b/.github/workflows/foundry.yml
index 1eb4dfc..364ca09 100644
--- a/.github/workflows/foundry.yml
+++ b/.github/workflows/foundry.yml
@@ -26,6 +26,9 @@ jobs:
           forge build --sizes
         id: build
 
+      - name: Check foundry.lock matches submodule pins
+        run: forge build --locked
+
       - name: Run Forge tests
         run: |
           forge test -vvv