diff --git a/core/Makefile b/core/Makefile
index f62e14ac1..76217b800 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -178,7 +178,7 @@ ifeq ($(DEBUG), 1)
 ASFLAGS += -g -ggdb
 endif
 
-CFLAGS = $(MCU) $(C_DEFS) $(C_INCLUDES) $(OPT) -Wall -Wno-missing-attributes -fasm -fdata-sections -ffunction-sections -Wno-stringop-overflow
+CFLAGS += $(MCU) $(C_DEFS) $(C_INCLUDES) $(OPT) -Wall -Wno-missing-attributes -fasm -fdata-sections -ffunction-sections -Wno-stringop-overflow
 
 CFLAGS += -g -ggdb