diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 780e89aa4..a652ee610 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -54,7 +54,7 @@ jobs:
       shell: bash -l {0}
       run: |
         pip install "traitlets>=4,<5"
-        pip install ipykernel==6.4.2
+        pip install ipykernel==5.5.5
         VOILA_TEST_DEBUG=1 VOILA_TEST_XEUS_CLING=1 py.test tests/ --async-test-timeout=240
         voila --help  # Making sure we can run `voila --help`
         # tests if voila sends a 'heartbeat' to avoid proxies from closing an apparently stale connection