diff --git a/arduino-mk/chipKIT.mk b/arduino-mk/chipKIT.mk
index baf7be4..42895cf 100644
--- a/arduino-mk/chipKIT.mk
+++ b/arduino-mk/chipKIT.mk
@@ -54,7 +54,7 @@ LDSCRIPT_FILE = $(ARDUINO_CORE_PATH)/$(LDSCRIPT)
 
 MCU_FLAG_NAME=mprocessor
 EXTRA_LDFLAGS  = -T$(ARDUINO_CORE_PATH)/$(LDSCRIPT)
-EXTRA_CXXFLAGS = -mno-smart-io -D$(BOARD)
+EXTRA_CPPFLAGS = -mno-smart-io -D$(BOARD)
 
 CHIPKIT_MK_PATH := $(dir $(lastword $(MAKEFILE_LIST)))