diff --git a/environment.yml b/environment.yml
index 02840803..2a2b05ec 100644
--- a/environment.yml
+++ b/environment.yml
@@ -29,4 +29,4 @@ dependencies:
   - snowballstemmer
   - sphinx
   - pip:
-    - sphinx_rtd_theme=0.2.4
+    - sphinx_rtd_theme==0.2.4