diff --git a/requirements.txt b/requirements.txt
index 7ae47e48981..ac5e7542c7b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -65,5 +65,6 @@ caniusepython3
 subprocess32
 flaky
 ldap3
+selectors2
 # setuptools_scm comes via tornado. newer versions of setuptools_scm do not support py2
 setuptools_scm<6.0