diff --git a/environment.yml b/environment.yml
index 1dbe4e86..8c132109 100644
--- a/environment.yml
+++ b/environment.yml
@@ -7,5 +7,6 @@ dependencies:
 - python=3.9.*
 - libgdal=3.4.*
 - sphinx-click
+- sphinx-rtd-theme
 - pip:
   - jinja2==3.0.3