diff --git a/docs/rtd_environment.yaml b/docs/rtd_environment.yaml
index f0fee16e1..aeebc4dff 100644
--- a/docs/rtd_environment.yaml
+++ b/docs/rtd_environment.yaml
@@ -6,3 +6,4 @@ dependencies:
  - python=3.11
  - pip
  - graphviz
+ - sphinx_rtd_theme>1.2.0