diff --git a/build/Arduino-Makefile/Arduino.mk b/build/Arduino-Makefile/Arduino.mk
index 8574b6d4..544a148c 100644
--- a/build/Arduino-Makefile/Arduino.mk
+++ b/build/Arduino-Makefile/Arduino.mk
@@ -399,8 +399,8 @@ ifndef OBJDUMP_NAME
 endif
 
 ifndef AR_NAME
-  # AR_NAME = avr-ar
-  AR_NAME = avr-gcc-ar
+  AR_NAME = avr-ar
+  # AR_NAME = avr-gcc-ar
 endif
 
 ifndef SIZE_NAME
diff --git a/build/Cosa.mk b/build/Cosa.mk
index 9180e463..670b2c4b 100644
--- a/build/Cosa.mk
+++ b/build/Cosa.mk
@@ -21,7 +21,7 @@ ifdef GCC_AVR_VER
   ARDUINO_VER = $(GCC_AVR_VER)
 else
   ifndef ARDUINO_VER
-    ARDUINO_VER = 1.6.5-r5
+    ARDUINO_VER = 1.6.6
   endif
   ifndef ARDUINO_DIR
     ARDUINO_DIR = $(HOME)/opt/arduino-$(ARDUINO_VER)