diff --git a/environment.yml b/environment.yml
index 1c1dd82f..9f416c0e 100644
--- a/environment.yml
+++ b/environment.yml
@@ -17,4 +17,5 @@ dependencies:
   - aiofiles>=0.3.0
   - websockets>=3.2
   - sphinxcontrib-asyncio>=0.2.0
+  - multidict>=4.0<5.0
   - https://github.com/channelcat/docutils-fork/zipball/master