diff --git a/pip/requirements.in b/pip/requirements.in
index d66356a2e..c2b3e8990 100644
--- a/pip/requirements.in
+++ b/pip/requirements.in
@@ -25,6 +25,8 @@ fluent-syntax
 # windows only
 psutil; sys.platform == "win32"
 pywin32; sys.platform == "win32"
+# pinned due to https://github.com/microsoft/xlang/issues/717
+# the latest version apparently works on python3.9
 winrt==1.0.20239.1; sys.platform == "win32" and platform_release == "10"
 
 # transitive windows dependencies