diff --git a/.github/workflows/deploy-book.yml b/.github/workflows/deploy-book.yml
index c89bd579..7bc45ce9 100644
--- a/.github/workflows/deploy-book.yml
+++ b/.github/workflows/deploy-book.yml
@@ -11,6 +11,9 @@ on:
     #
     # paths:
     # - some-subfolder/**
+  pull_request:
+    branches:
+    - main
     
 env:
   CACHE_NUMBER: 1  # increase to reset cache manually
diff --git a/docs/environment.yml b/docs/environment.yml
index cd99a382..1bc1e131 100644
--- a/docs/environment.yml
+++ b/docs/environment.yml
@@ -22,13 +22,14 @@ dependencies:
   - halo # optional
   - plotly # optional
   - jupyter-book # for docs
-  - sphinx # for docs
+  - sphinx<5.0 # for docs
   - sphinx-book-theme # for docs
   - sphinx-autoapi
   - autodoc-pydantic # for docs
   - nbsphinx-link
   - sphinxcontrib-mermaid
   - sphinx-panels
+  - sphinxcontrib-serializinghtml==1.1.5  # Can remove once updated to sphinx>=5.0
   - nbclient>=0.7.4
   - pip
   - pip: