diff --git a/libraries/AP_GPS/examples/GPS_MTK_test/GPS_MTK_test.pde b/libraries/AP_GPS/examples/GPS_MTK_test/GPS_MTK_test.pde
index ab9a0b3721..9de621e309 100644
--- a/libraries/AP_GPS/examples/GPS_MTK_test/GPS_MTK_test.pde
+++ b/libraries/AP_GPS/examples/GPS_MTK_test/GPS_MTK_test.pde
@@ -9,6 +9,7 @@
 #include <FastSerial.h>
 #include <AP_Common.h>
 #include <AP_GPS.h>
+#include <AP_Math.h>
 
 FastSerialPort0(Serial);
 FastSerialPort1(Serial1);