diff --git a/.github/workflows/deploy-pages.yml b/.github/workflows/deploy-pages.yml
index 595bf9166..980574c45 100644
--- a/.github/workflows/deploy-pages.yml
+++ b/.github/workflows/deploy-pages.yml
@@ -10,7 +10,7 @@ concurrency:
 
 jobs:
   deploy:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - name: Use Node.js
@@ -29,7 +29,7 @@ jobs:
           sudo apt-get update -y
           sudo apt-get install -y texlive texlive-fonts-extra latexmk
       - name: Fetch Yarn dependencies
-        run: yarn install
+        run: yarn install --frozen-lockfile
       - name: Build
         run: |
           set -euxo pipefail
diff --git a/package.json b/package.json
index 4c54381ad..b6fa51e3d 100644
--- a/package.json
+++ b/package.json
@@ -24,6 +24,7 @@
     "url": "https://github.com/source-academy/sicp/issues"
   },
   "homepage": "https://sourceacademy.org/sicpjs",
+  "packageManager": "yarn@1.22.22+sha1.ac34549e6aa8e7ead463a7407e1c7390f61a6610",
   "devDependencies": {
     "@babel/core": "^7.27.4",
     "@babel/node": "^7.27.1",