diff --git a/conf/firmwares/subsystems/rotorcraft/telemetry_transparent_usb.makefile b/conf/firmwares/subsystems/rotorcraft/telemetry_transparent_usb.makefile
index f6cb031760..b50ed3f18e 100644
--- a/conf/firmwares/subsystems/rotorcraft/telemetry_transparent_usb.makefile
+++ b/conf/firmwares/subsystems/rotorcraft/telemetry_transparent_usb.makefile
@@ -10,7 +10,7 @@ ap.srcs += $(SRC_ARCH)/usb_ser_hw.c $(SRC_ARCH)/lpcusb/usbhw_lpc.c $(SRC_ARCH)/l
 ap.srcs += $(SRC_ARCH)/lpcusb/usbstdreq.c $(SRC_ARCH)/lpcusb/usbinit.c
 else
 ifeq ($(ARCH), stm32)
-ap.CFLAGS += -DDOWNLINK -DPERIODIC_TELEMETRY -DDOWNLINK_DEVICE=usb_serial -DPPRZ_UART=UsbS
+ap.CFLAGS += -DDOWNLINK -DPERIODIC_TELEMETRY -DDOWNLINK_DEVICE=usb_serial -DPPRZ_UART=usb_serial
 ap.CFLAGS += -DDOWNLINK_TRANSPORT=pprz_tp -DDATALINK=PPRZ -DUSE_USB_SERIAL -DDefaultPeriodic='&telemetry_Main'
 ap.srcs += subsystems/datalink/downlink.c subsystems/datalink/pprz_transport.c subsystems/datalink/telemetry.c
 ap.srcs += $(SRC_FIRMWARE)/datalink.c $(SRC_FIRMWARE)/rotorcraft_telemetry.c