diff --git a/docs/conda_env.yml b/docs/conda_env.yml
index 52f7498..06173de 100644
--- a/docs/conda_env.yml
+++ b/docs/conda_env.yml
@@ -16,5 +16,6 @@ dependencies:
     - matplotlib
     - sphinx_autodoc_typehints
     - stable-baselines3>=1.2.0
+    - sphinx>=4.2
     # See https://github.com/readthedocs/sphinx_rtd_theme/issues/1115
     - sphinx_rtd_theme>=1.0