diff --git a/libraries/AP_Compass/AP_Compass_Backend.h b/libraries/AP_Compass/AP_Compass_Backend.h
index 0f11a4e141..988f0bb630 100644
--- a/libraries/AP_Compass/AP_Compass_Backend.h
+++ b/libraries/AP_Compass/AP_Compass_Backend.h
@@ -50,6 +50,7 @@ public:
       calibration values invalid then this number must be changed.
      */
     enum DevTypes {
+        DEVTYPE_HMC5883_OLD = 0x01,
         DEVTYPE_HMC5883 = 0x07,
         DEVTYPE_LSM303D = 0x02,
         DEVTYPE_AK8963  = 0x04,