diff --git a/BUILD.md b/BUILD.md
index b505412..d48b813 100644
--- a/BUILD.md
+++ b/BUILD.md
@@ -472,6 +472,9 @@ scanning over all enabled modes, and you could have some detection delay. Enable
 - #define SERIAL_REPEATER: enable a second serial port (USART2, pins PA2 and PA3) for Nextion
 LCD display.
 
+- #define SERIAL_REPEATER_USART1: enable USART1 (pins PA9 and PA10) for Nextion LCD display. Do
+not use with STM32_USART1_HOST enabled, only with USB host communication.
+
 - #define ENABLE_P25_WIDE: enable support for Motorola Wide P25 mod/demod in XTS3000 radios. Using
 this mode improves RX BER. You need to enable this mode in your radio for each conventional
 personalities.