diff --git a/libraries/AP_GPS/AP_GPS_config.h b/libraries/AP_GPS/AP_GPS_config.h
index 6b114f156a..08ebdac605 100644
--- a/libraries/AP_GPS/AP_GPS_config.h
+++ b/libraries/AP_GPS/AP_GPS_config.h
@@ -35,15 +35,16 @@
 
 #if !defined(AP_GPS_BLENDED_ENABLED) && defined(GPS_MAX_INSTANCES)
 #define AP_GPS_BLENDED_ENABLED AP_GPS_BACKEND_DEFAULT_ENABLED && GPS_MAX_INSTANCES > GPS_MAX_RECEIVERS
-#if AP_GPS_BLENDED_ENABLED
-#define GPS_BLENDED_INSTANCE GPS_MAX_RECEIVERS  // the virtual blended GPS is always the highest instance (2)
-#endif
 #endif
 
 #ifndef AP_GPS_BLENDED_ENABLED
 #define AP_GPS_BLENDED_ENABLED 0
 #endif
 
+#if AP_GPS_BLENDED_ENABLED
+#define GPS_BLENDED_INSTANCE GPS_MAX_RECEIVERS  // the virtual blended GPS is always the highest instance (2)
+#endif
+
 #ifndef AP_GPS_DRONECAN_ENABLED
 #define AP_GPS_DRONECAN_ENABLED AP_GPS_BACKEND_DEFAULT_ENABLED && HAL_ENABLE_DRONECAN_DRIVERS
 #endif