diff --git a/firmware/config/boards/proteus/board.mk b/firmware/config/boards/proteus/board.mk
index 2a8ddacfa2..3f070b58d8 100644
--- a/firmware/config/boards/proteus/board.mk
+++ b/firmware/config/boards/proteus/board.mk
@@ -68,6 +68,8 @@ ifeq ($(PROJECT_CPU),ARCH_STM32F7)
 else ifeq ($(PROJECT_CPU),ARCH_STM32F4)
 	DDEFS += -DSTATIC_BOARD_ID=STATIC_BOARD_ID_PROTEUS_F4
 	DDEFS += -DRAM_UNUSED_SIZE=100
+	# todo: https://github.com/rusefi/rusefi/pull/7505
+	# you would think that removal of below like would reduce flash usage but somehow it increased it somehow?!
 	DDEFS += -DKNOCK_SPECTROGRAM=TRUE
 else ifeq ($(PROJECT_CPU),ARCH_STM32H7)
 	DDEFS += -DSTATIC_BOARD_ID=STATIC_BOARD_ID_PROTEUS_H7