diff --git a/mcu_utils/fw/README.md b/mcu_utils/fw/README.md
new file mode 100644
index 00000000000..b78329771af
--- /dev/null
+++ b/mcu_utils/fw/README.md
@@ -0,0 +1,3 @@
+Warning!
+fancyblink and stm32f4-stock firmware doesn't work on our
+STM32F407G-DISC board.