diff --git a/.github/workflows/deploy-github-page.yml b/.github/workflows/deploy-github-page.yml
index a8ce22e3..5c31f9d5 100644
--- a/.github/workflows/deploy-github-page.yml
+++ b/.github/workflows/deploy-github-page.yml
@@ -70,7 +70,7 @@ jobs:
         shell: bash -l {0}
         run: |
           set -e
-          micromamba create -n xeus-lite-host jupyterlite-core jupyter_server
+          micromamba create -n xeus-lite-host jupyterlite-core=0.6 jupyter_server
           micromamba activate xeus-lite-host
           cd build/test
           # Fresh install browsers, and run Emscripten tests in them
@@ -141,7 +141,7 @@ jobs:
         shell: bash -l {0}
         run: |
           micromamba activate xeus-lite-host
-          python -m pip install jupyterlite-xeus
+          python -m pip install jupyterlite-xeus=4.0.0rc0
           jupyter lite build \
               --XeusAddon.prefix=${{ env.PREFIX }} \
               --contents README.md \