diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index f34e206..198b7f9 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -117,7 +117,8 @@ jobs:
         auto-update-conda: false
     - name: Install Jupyterbook and ruamel.yaml
       run: |
-        conda install jupyter-book ruamel.yaml sphinx-autosummary-accessors -c conda-forge
+        # The docs use the Jupyter Book 1.x Sphinx project layout.
+        conda install "jupyter-book<2" ruamel.yaml sphinx-autosummary-accessors -c conda-forge
     - name: Install sharrow
       run: |
         python -m pip install --no-deps .
diff --git a/docs/requirements.txt b/docs/requirements.txt
index 09e8b90..6162bd0 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,4 +1,4 @@
-jupyter-book
+jupyter-book < 2
 matplotlib
 numpy >= 1.19
 pandas >= 1.2