diff --git a/environment.yml b/environment.yml
index f6f74518..02840803 100644
--- a/environment.yml
+++ b/environment.yml
@@ -29,4 +29,4 @@ dependencies:
   - snowballstemmer
   - sphinx
   - pip:
-    - sphinx_rtd_theme
+    - sphinx_rtd_theme=0.2.4