diff --git a/src/hw/booster.md b/src/hw/booster.md
index 681f110..ccf5d1f 100644
--- a/src/hw/booster.md
+++ b/src/hw/booster.md
@@ -12,10 +12,11 @@
 git clone git@github.com:quartiq/booster.git
 cd booster
 nix-shell -p rustup cargo rustc dfu-util
+rustup target add thumbv7em-none-eabihf
 cargo install cargo-binutils
 rustup component add llvm-tools-preview
 cargo build --release
-cargo objcopy -- -O binary booster.bin
+cargo objcopy --release -- -O binary booster.bin
 # enter dfu mode by either serial terminal or
 # press `DFU Bootloader` button while rebooting
 dfu-util -a 0 -s 0x08000000:leave --download booster.bin