diff --git a/requirements.txt b/requirements.txt
index c103380..eeaa138 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ iso8601==0.1.12
 pytest==5.4.3
 pytest-asyncio==0.12.0
 httptools>=0.1.1
+contextvars==2.4;python_version<"3.7"