diff --git a/arduino-mk/Arduino.mk b/arduino-mk/Arduino.mk
index dc8aa6c..f12637d 100644
--- a/arduino-mk/Arduino.mk
+++ b/arduino-mk/Arduino.mk
@@ -285,9 +285,11 @@ ifdef ARDUINO_DIR
 
 ifndef AVR_TOOLS_DIR
 AVR_TOOLS_DIR     = $(ARDUINO_DIR)/hardware/tools/avr
-# The avrdude bundled with Arduino can't find it's config
+# The avrdude bundled with Arduino can't find its config
+ifndef AVRDUDE_CONF
 AVRDUDE_CONF	  = $(AVR_TOOLS_DIR)/etc/avrdude.conf
 endif
+endif
 
 ifndef AVR_TOOLS_PATH
 AVR_TOOLS_PATH    = $(AVR_TOOLS_DIR)/bin