diff --git a/libraries/APM_Control/AR_AttitudeControl.cpp b/libraries/APM_Control/AR_AttitudeControl.cpp
index f1f9521a12..bc05b1b953 100644
--- a/libraries/APM_Control/AR_AttitudeControl.cpp
+++ b/libraries/APM_Control/AR_AttitudeControl.cpp
@@ -601,7 +601,7 @@ bool AR_AttitudeControl::get_forward_speed(float &speed) const
     if (!_ahrs.get_velocity_NED(velocity)) {
         // use less accurate GPS, assuming entire length is along forward/back axis of vehicle
         if (AP::gps().status() >= AP_GPS::GPS_OK_FIX_3D) {
-            if (fabsf(wrap_180_cd(_ahrs.yaw_sensor - AP::gps().ground_course_cd())) <= 9000) {
+            if (abs(wrap_180_cd(_ahrs.yaw_sensor - AP::gps().ground_course_cd())) <= 9000) {
                 speed = AP::gps().ground_speed();
             } else {
                 speed = -AP::gps().ground_speed();