diff --git a/environment.yml b/environment.yml
index b825df22..7499c25d 100644
--- a/environment.yml
+++ b/environment.yml
@@ -26,4 +26,4 @@ dependencies:
   - six
   - snowballstemmer
   - sphinx
-  - sphinx_rtd_theme
+  - sphinx_rtd_theme=0.2.5b1