diff --git a/libraries/AP_AHRS/AP_AHRS_Backend.h b/libraries/AP_AHRS/AP_AHRS_Backend.h
index a3c079d5e8..a39f66ba45 100644
--- a/libraries/AP_AHRS/AP_AHRS_Backend.h
+++ b/libraries/AP_AHRS/AP_AHRS_Backend.h
@@ -300,7 +300,7 @@ public:
     }
 
     // get_variances - provides the innovations normalised using the innovation variance where a value of 0
-    // indicates perfect consistency between the measurement and the EKF solution and a value of of 1 is the maximum
+    // indicates perfect consistency between the measurement and the EKF solution and a value of 1 is the maximum
     // inconsistency that will be accepted by the filter
     // boolean false is returned if variances are not available
     virtual bool get_variances(float &velVar, float &posVar, float &hgtVar, Vector3f &magVar, float &tasVar) const {