diff --git a/requirements.txt b/requirements.txt
index 7deef88..9bdef65 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1,2 @@
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
+typing-extensions>=4.1.0 # PSF-2.0