diff --git a/firmware/ice40-riscv/icE1usb/Makefile b/firmware/ice40-riscv/icE1usb/Makefile
index 05fca43..f2b1103 100644
--- a/firmware/ice40-riscv/icE1usb/Makefile
+++ b/firmware/ice40-riscv/icE1usb/Makefile
@@ -10,7 +10,7 @@
 DFU_UTIL = dfu-util
 
 BOARD_DEFINE=BOARD_$(shell echo $(BOARD) | tr a-z\- A-Z_)
-CFLAGS=-Wall -Os -march=rv32i -mabi=ilp32 -ffreestanding -flto -nostartfiles -fomit-frame-pointer -Wl,--gc-section --specs=nano.specs -D$(BOARD_DEFINE) -I. -I../common
+CFLAGS=-Wall -Wextra -Wno-unused -Os -march=rv32i -mabi=ilp32 -ffreestanding -flto -nostartfiles -fomit-frame-pointer -Wl,--gc-section --specs=nano.specs -D$(BOARD_DEFINE) -I. -I../common
 
 NO2USB_FW_VERSION=0
 include ../../../gateware/cores/no2usb/fw/fw.mk