diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3bfb808..52e0bcc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -24,6 +24,9 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: "22"
-      - run: npm install --no-audit --no-fund
+      # `npm ci` rather than `npm install`: it installs the lockfile exactly
+      # and fails when package.json and package-lock.json disagree, so CI
+      # tests the tree a fresh clone would get (MX-222).
+      - run: npm ci --no-audit --no-fund
       - run: npm run typecheck
       - run: npm test