diff --git a/.readthedocs.yml b/.readthedocs.yaml
similarity index 68%
rename from .readthedocs.yml
rename to .readthedocs.yaml
index 0d4ef42..f792ab5 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yaml
@@ -3,6 +3,8 @@ version: 2
 build:
   os: "ubuntu-20.04"
   tools:
+    # sphinx-js isn't compatible with python 3.10.
+    # https://github.com/mozilla/sphinx-js/issues/186
     python: "3.9"
     nodejs: "16"
 
diff --git a/docs/requirements.txt b/docs/requirements.txt
index fc516d5..2791fe4 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,7 +1,11 @@
-sphinx==3.5.1
-docutils==0.16.0
-sphinx-prompt==1.1.0
-sphinx-tabs==2.0.1
+sphinx==4.4.0
+sphinx-prompt==1.5.0
+sphinx-tabs==3.2.0
 sphinx-rtd-theme==1.0.0
-sphinx-notfound-page==0.3
+sphinx-notfound-page==0.8
 sphinx-js==3.1
+
+# sphinx-js pins jinja to a version that doesn't
+# pin its version of markupsafe, markupsafe>=2.1
+# isn't compatible with that version of jinja.
+markupsafe==2.0.1