diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d2076e0a1..8ca8bce00 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -59,7 +59,7 @@ jobs:
             ${{ runner.os }}-yarn-
 
       - name: Install dependencies
-        run: python -m pip install -U jupyter_packaging~=0.7.9 jupyterlab~=3.0 pip wheel build
+        run: python -m pip install -U jupyter_packaging~=0.7.9 jupyterlab~=3.0 pip wheel
       - name: Test the extension
         run: |
           jlpm
diff --git a/ui-tests/docker/prepare.sh b/ui-tests/docker/prepare.sh
index c1b19172e..c41179adb 100755
--- a/ui-tests/docker/prepare.sh
+++ b/ui-tests/docker/prepare.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-yarn install
+yarn install --frozen-lockfile
 
 echo Will run 'wait-for-it' $*
 $(dirname $0)/wait-for-it.sh $*