diff --git a/Makefile b/Makefile
index 2440860..f5af301 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@
 F_CPU = 16000000UL
 TARGET = main
 CC = avr-gcc
-INCLUDES = -I../../headers/
+INCLUDES ?= -I../../headers/ # ?= : dont define if already defined
 
 AVRGCC_MCU_TYPE = atmega328p
 AVRDUDE_MCU_TYPE = m328p
@@ -80,4 +80,4 @@ dump:
 clean:
 	rm -f main.hex main.bin *.o
 
-.PHONY : all clean hex flash restore
\ No newline at end of file
+.PHONY : all clean hex flash restore