diff --git a/firmware/config/boards/f407-discovery/config.mk b/firmware/config/boards/f407-discovery/config.mk
new file mode 100644
index 0000000000..11f7c985d8
--- /dev/null
+++ b/firmware/config/boards/f407-discovery/config.mk
@@ -0,0 +1 @@
+PROJECT_CPU = ARCH_STM32F4
\ No newline at end of file
diff --git a/firmware/rusefi.mk b/firmware/rusefi.mk
index 6aa06704c0..9bab68fa9d 100644
--- a/firmware/rusefi.mk
+++ b/firmware/rusefi.mk
@@ -19,10 +19,7 @@ ifeq ($(PROJECT_BOARD),)
   PROJECT_BOARD = f407-discovery
 endif
 
-ifeq ($(PROJECT_CPU),)
-  PROJECT_CPU = ARCH_STM32F4
-endif
-
+# minus before 'include' makes this directive optional, we will be good without config.mk file
 -include $(PROJECT_DIR)/config/boards/$(PROJECT_BOARD)/config.mk
 
 # CPU-dependent defs