diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h
index 3bafdb5fc4aac8a3059114fc53aaf8b2b990afe9..b6fd4e73c4360eab9e12a8b12d7093553a7c02b5 100644
--- a/cores/arduino/Arduino.h
+++ b/cores/arduino/Arduino.h
@@ -35,6 +35,7 @@ typedef uint16_t word;
 //
 #include "avr/pgmspace.h"
 #include "avr/interrupt.h"
+#include "avr/io.h"
 
 #include "binary.h"
 #include "itoa.h"
diff --git a/cores/arduino/avr/io.h b/cores/arduino/avr/io.h
new file mode 100644
index 0000000000000000000000000000000000000000..33d20cdd261558b2e627d4a6d2fc2d69a2e5f881
--- /dev/null
+++ b/cores/arduino/avr/io.h
@@ -0,0 +1,32 @@
+/*
+  io.h - Definitions for compatibility with AVR io macros
+
+  Copyright (c) 2016 Arduino LLC
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+  THE SOFTWARE
+*/
+
+#ifndef _IO_H_
+#define _IO_H_
+
+#define RAMSTART (HMCRAMC0_ADDR)
+#define RAMSIZE  (HMCRAMC0_SIZE)
+#define RAMEND   (RAMSTART + RAMSIZE - 1)
+
+#endif