1 files changed, 1 insertions, 0 deletions

diff --git a/setup.cfg b/setup.cfg
index 792a35d6e..cdd9894d6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -40,6 +40,7 @@ package_dir =
 
 install_requires =
     importlib-metadata;python_version<"3.8"
+    greenlet != 0.4.17;python_version>="3"
 
 [options.extras_require]
 asyncio =