diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 739c3a0..65d37ca 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -32,5 +32,12 @@ jobs:
             example=${dir%/}
             [ -f "$example/compose.yml" ] || continue
             docker compose -f "$example/compose.yml" config --quiet || status=1
+            # The on-chain overlay is the one nobody runs before merging: it needs
+            # a wallet, an RPC and a keystore. Interpolating .env.example also
+            # proves that file still lists every variable the overlay reads.
+            [ -f "$example/compose.onchain.yml" ] || continue
+            docker compose --env-file "$example/.env.example" \
+              -f "$example/compose.yml" -f "$example/compose.onchain.yml" \
+              config --quiet || status=1
           done
           exit $status