diff --git a/.readthedocs_env.yml b/.readthedocs_env.yml
index 72ca5299..0cab3567 100644
--- a/.readthedocs_env.yml
+++ b/.readthedocs_env.yml
@@ -13,6 +13,7 @@ dependencies:
   - jupyterlab_widgets
   - krb5
   - lxml
+  - ipykernel
   - matplotlib
   - nbclassic
   - nodejs
diff --git a/ci/azure-build-and-test.yml b/ci/azure-build-and-test.yml
index b3504e92..962bb45f 100644
--- a/ci/azure-build-and-test.yml
+++ b/ci/azure-build-and-test.yml
@@ -230,7 +230,7 @@ jobs:
       source activate-conda.sh
       conda activate build
       set -x
-      \conda install -y astropy astropy-sphinx-theme jupyter_sphinx numpydoc sphinx sphinx-automodapi
+      \conda install -y astropy astropy-sphinx-theme ipykernel jupyter_sphinx nbclassic numpydoc sphinx sphinx-automodapi
       cd docs
       make html
     displayName: Build docs
diff --git a/setup.py b/setup.py
index 46e850de..99a314e9 100755
--- a/setup.py
+++ b/setup.py
@@ -133,6 +133,7 @@
         ],
         "docs": [
             "astropy-sphinx-theme",
+            "ipykernel",
             "sphinx>=1.6",
             "sphinx-automodapi",
             "numpydoc",