diff --git a/libraries/AP_Compass/AP_Compass_AK8963.cpp b/libraries/AP_Compass/AP_Compass_AK8963.cpp
index 3b6f3554cf..1ecb408057 100644
--- a/libraries/AP_Compass/AP_Compass_AK8963.cpp
+++ b/libraries/AP_Compass/AP_Compass_AK8963.cpp
@@ -299,7 +299,7 @@ AP_Compass_AK8963::AP_Compass_AK8963(Compass &compass) :
     AP_Compass_Backend(compass),    
     _backend(NULL),
     _initialised(false),
-    _state(CONVERSION),
+    _state(STATE_CONVERSION),
     _last_update_timestamp(0),
     _last_accum_time(0)
 {
@@ -458,15 +458,15 @@ void AP_Compass_AK8963::_update()
 
     switch (_state)
        {
-        case CONVERSION:
+        case STATE_CONVERSION:
             _start_conversion();
-            _state = SAMPLE;
+            _state = STATE_SAMPLE;
             break;
-        case    SAMPLE:
+        case STATE_SAMPLE:
             _collect_samples();
-            _state = CONVERSION;
+            _state = STATE_CONVERSION;
             break;
-        case ERROR:
+        case STATE_ERROR:
             break;
         default:
             break;
diff --git a/libraries/AP_Compass/AP_Compass_AK8963.h b/libraries/AP_Compass/AP_Compass_AK8963.h
index d185cd8aa8..c5c5a2aa4e 100644
--- a/libraries/AP_Compass/AP_Compass_AK8963.h
+++ b/libraries/AP_Compass/AP_Compass_AK8963.h
@@ -54,9 +54,9 @@ protected:
 private:
     typedef enum 
     {
-        CONVERSION,
-        SAMPLE,
-        ERROR
+        STATE_CONVERSION,
+        STATE_SAMPLE,
+        STATE_ERROR
     } state_t;
 
     virtual bool        _backend_init() = 0;