diff --git a/nuttx-configs/tap-v1/nsh/defconfig b/nuttx-configs/tap-v1/nsh/defconfig
index cd5cd6b9be..f824be141c 100644
--- a/nuttx-configs/tap-v1/nsh/defconfig
+++ b/nuttx-configs/tap-v1/nsh/defconfig
@@ -885,6 +885,9 @@ CONFIG_SERIAL_NPOLLWAITERS=2
 CONFIG_SERIAL_IFLOWCONTROL=y
 CONFIG_SERIAL_OFLOWCONTROL=y
 # CONFIG_SERIAL_DMA is not set
+CONFIG_SERIAL_IFLOWCONTROL_WATERMARKS=y
+CONFIG_SERIAL_IFLOWCONTROL_LOWER_WATERMARK=10
+CONFIG_SERIAL_IFLOWCONTROL_UPPER_WATERMARK=90
 CONFIG_ARCH_HAVE_SERIAL_TERMIOS=y
 # CONFIG_USART1_SERIAL_CONSOLE is not set
 # CONFIG_USART2_SERIAL_CONSOLE is not set