diff --git a/libraries/Wire/src/Wire.cpp b/libraries/Wire/src/Wire.cpp
index 99b1cc4ead..74037f709b 100644
--- a/libraries/Wire/src/Wire.cpp
+++ b/libraries/Wire/src/Wire.cpp
@@ -27,6 +27,10 @@ extern "C" {
 
 #include "Wire.h"
 
+// Distinguish master from slave.
+// 0x01 is a reserved value, and thus cannot be used by slave devices
+static const uint8_t MASTER_ADDRESS = 0x01;
+
 // Constructors ////////////////////////////////////////////////////////////////
 
 TwoWire::TwoWire()
diff --git a/libraries/Wire/src/Wire.h b/libraries/Wire/src/Wire.h
index dfeccfdd6d..dfba0aba69 100644
--- a/libraries/Wire/src/Wire.h
+++ b/libraries/Wire/src/Wire.h
@@ -30,8 +30,6 @@ extern "C" {
 
 #define BUFFER_LENGTH 32
 
-#define MASTER_ADDRESS 0x33
-
 // WIRE_HAS_END means Wire has end()
 #define WIRE_HAS_END 1