diff --git a/libraries/AP_Compass/AP_Compass_RM3100.cpp b/libraries/AP_Compass/AP_Compass_RM3100.cpp
index b191a6b52b..7e4fd7970b 100644
--- a/libraries/AP_Compass/AP_Compass_RM3100.cpp
+++ b/libraries/AP_Compass/AP_Compass_RM3100.cpp
@@ -61,7 +61,6 @@
 #define GAIN_CC50 20.0f   // LSB/uT
 #define GAIN_CC100 38.0f
 #define GAIN_CC200 75.0f
-#define UTESLA_TO_MGAUSS   10.0f // uT to mGauss conversion
 
 #define TMRC    0x94    // Update rate 150Hz
 #define CMM     0x71    // read 3 axes and set data ready if 3 axes are ready