diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index db7d8dd6e..fe201b58e 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -32,7 +32,18 @@ jobs:
       run: npm run build-module --no-typecheck
     - name: Build Python client bundles
       run: npm run build-python --no-typecheck
-    - run: sudo apt-get install firefox xvfb
+    - run: |
+        sudo add-apt-repository ppa:mozillateam/ppa
+        echo '
+        Package: *
+        Pin: release o=LP-PPA-mozillateam
+        Pin-Priority: 1001
+
+        Package: firefox
+        Pin: version 1:1snap1-0ubuntu2
+        Pin-Priority: -1
+        ' | sudo tee /etc/apt/preferences.d/mozilla-firefox
+        sudo apt-get install firefox xvfb
       if: startsWith(runner.os, 'Linux')
     - name: Run JavaScript tests (including WebGL)
       # Swiftshader, used by Chrome headless, crashes when running Neuroglancer
@@ -99,8 +110,19 @@ jobs:
     - run: npm run build-python -- --no-typecheck
     - name: Install Python packaging/test tools
       run: python -m pip install --upgrade pip tox wheel numpy pytest
-    - run: sudo apt-get install -y firefox xvfb
-      if: ${{ startsWith(runner.os, 'Linux') }}
+    - run: |
+        sudo add-apt-repository ppa:mozillateam/ppa
+        echo '
+        Package: *
+        Pin: release o=LP-PPA-mozillateam
+        Pin-Priority: 1001
+
+        Package: firefox
+        Pin: version 1:1snap1-0ubuntu2
+        Pin-Priority: -1
+        ' | sudo tee /etc/apt/preferences.d/mozilla-firefox
+        sudo apt-get install firefox xvfb
+      if: startsWith(runner.os, 'Linux')
     - name: Test with tox
       run: tox -e ${{ fromJSON('["skip-browser-tests","firefox-xvfb"]')[runner.os == 'Linux'] }}
       env: