diff --git a/libraries/AP_Math/location.cpp b/libraries/AP_Math/location.cpp
index 2d6f57f516..7035ce59da 100644
--- a/libraries/AP_Math/location.cpp
+++ b/libraries/AP_Math/location.cpp
@@ -31,7 +31,7 @@ static float longitude_scale(const struct Location *loc)
 {
 	static int32_t last_lat;
 	static float scale = 1.0;
-	if (abs(last_lat - loc->lat) < 100000) {
+	if (labs(last_lat - loc->lat) < 100000) {
 		// we are within 0.01 degrees (about 1km) of the
 		// same latitude. We can avoid the cos() and return
 		// the same scale factor.