diff --git a/README.md b/README.md
index a11d5cf..44e5955 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,8 @@ Sound level monitoring via USB Benetech GM1356.
 Named after [Loud Howard](https://dilbert.com/strip/1995-04-21).
 
 Requirements:
- - [vdirsyncer](http://vdirsyncer.pimutils.org/en/stable/)
-
+ - [hidapi](https://github.com/libusb/hidapi)
+ - An OS which recognises the GM1356 as a USB device (ie. not OSX Big Sur).
 
 # Usage