diff --git a/README.md b/README.md
index 5bf98b7..dae0a22 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ There is no input function. It can be easily added, but I didn't need it.
 The device appears as a USB-serial ttyACMx. Write characters to it. Everything works in character mode.
 There's no harm in sending CRLF, these are discarded with no reply.
 
-- Uppercase letters turn GPIOs on, their lowercase counterparts turn them on.
+- Uppercase letters turn GPIOs on, their lowercase counterparts turn them off.
 - Valid commands return the same character back. Unknown commands return "?".
 - "0" turns all *off*, "1" turns all *on*. This is handy if you need just one signal, or want to shut everything down.