diff --git a/legacy/README.md b/legacy/README.md
index f7e4fb365..072f77637 100644
--- a/legacy/README.md
+++ b/legacy/README.md
@@ -54,6 +54,8 @@ Step 3 should produce the same sha256 fingerprint like your local build (for the
 1. Install python-trezor: `pip install trezor` ([more info](https://github.com/trezor/python-trezor))
 2. `trezorctl firmware_update -f build/trezor-TAG.bin`
 
+*Note: if your device is on the latest bootloader version and you flash custom firmware then you will receive a hard fault warning when booting the firmware image. To avoid this issue, just remove the code in startup.s added by [this commit](https://github.com/trezor/trezor-firmware/commit/222c9ea46c7574cb52d4713c481438a32b85e692#diff-178d0ab7c4debbcf430a0fad8fa06a5c).*
+
 ## Building for development
 
 If you want to build device firmware, make sure you have the