diff --git a/Makefile b/Makefile
index 9e20a43..4730672 100644
--- a/Makefile
+++ b/Makefile
@@ -34,6 +34,10 @@
 SOURCE    = main.c motion_control.c gcode.c spindle_control.c coolant_control.c serial.c \
              protocol.c stepper.c eeprom.c settings.c planner.c nuts_bolts.c limits.c jog.c\
              print.c probe.c report.c system.c
+ifeq ($(USE_ADC), 1)
+	CPPFLAGS += -DUSE_ADC
+	SOURCE += adc.c
+endif
 BUILDDIR = build
 SOURCEDIR = grbl
 # FUSES      = -U hfuse:w:0xd9:m -U lfuse:w:0x24:m
@@ -47,7 +51,7 @@
 # COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections
 
 # Compile flags for avr-gcc v4.9.2 compatible with the IDE. Or if you don't care about the warnings. 
-COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections -flto
+COMPILE = avr-gcc -Wall -Os $(CPPFLAGS) -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections -flto
 
 
 OBJECTS = $(addprefix $(BUILDDIR)/,$(notdir $(SOURCE:.c=.o)))