diff --git a/EKF/ekf.h b/EKF/ekf.h
index 30801ad6dd..5fca7e4c65 100644
--- a/EKF/ekf.h
+++ b/EKF/ekf.h
@@ -121,6 +121,8 @@ public:
 	// return the estimated terrain vertical position relative to the NED origin
 	bool get_terrain_vert_pos(float *ret);
 
+	void get_accel_bias(float *bias) {*bias = _state.accel_z_bias;}
+
 private:
 
 	static const uint8_t _k_num_states = 24;
diff --git a/EKF/estimator_interface.h b/EKF/estimator_interface.h
index 22f4b58840..6579c8eeeb 100644
--- a/EKF/estimator_interface.h
+++ b/EKF/estimator_interface.h
@@ -209,10 +209,7 @@ public:
 		*val = _mag_declination_to_save_deg;
 	}
 
-	void copy_accel_bias(float *bias)
-	{
-		*bias = _state[15];
-	}
+	virtual void get_accel_bias(float *bias) = 0;
 
 protected: