diff --git a/README.md b/README.md
index 25af0497..5108a87f 100644
--- a/README.md
+++ b/README.md
@@ -113,6 +113,7 @@ The [Functions](https://pit-ray.github.io/win-vind/cheat_sheet/functions/) page
 
 ## Known Issues
 - EasyClick does not seem to work properly for some applications on older Windows 10 before 1803. The cause is not known, but we have confirmed that it works after 1909. ([#11](https://github.com/pit-ray/win-vind/issues/11))
+- Windows 10/11 Single Language does not seem to be able to map toggle keys such as `<Capslock>`. ([#40](https://github.com/pit-ray/win-vind/issues/40))
 
 ## Contribute
 If you would like to contribute to win-vind, see [CONTRIBUTING.md](https://github.com/pit-ray/win-vind/blob/master/CONTRIBUTING.md).