diff --git a/libraries/AP_GPS/AP_GPS_GSOF.cpp b/libraries/AP_GPS/AP_GPS_GSOF.cpp
index 43fd72c562..3026e5791f 100644
--- a/libraries/AP_GPS/AP_GPS_GSOF.cpp
+++ b/libraries/AP_GPS/AP_GPS_GSOF.cpp
@@ -18,6 +18,8 @@
 //  Code by Michael Oborne
 //
 
+#define ALLOW_DOUBLE_MATH_FUNCTIONS
+
 #include "AP_GPS.h"
 #include "AP_GPS_GSOF.h"
 #include <DataFlash/DataFlash.h>
diff --git a/libraries/AP_GPS/AP_GPS_SBF.cpp b/libraries/AP_GPS/AP_GPS_SBF.cpp
index 641c219ea8..e086ea878f 100644
--- a/libraries/AP_GPS/AP_GPS_SBF.cpp
+++ b/libraries/AP_GPS/AP_GPS_SBF.cpp
@@ -18,6 +18,8 @@
 //  Code by Michael Oborne
 //
 
+#define ALLOW_DOUBLE_MATH_FUNCTIONS
+
 #include "AP_GPS.h"
 #include "AP_GPS_SBF.h"
 #include <DataFlash/DataFlash.h>