diff --git a/ArduSub/Sub.h b/ArduSub/Sub.h
index 2f669b72e5..6b992bac1c 100644
--- a/ArduSub/Sub.h
+++ b/ArduSub/Sub.h
@@ -37,7 +37,6 @@
 #include <AP_Declination/AP_Declination.h>     // ArduPilot Mega Declination Helper Library
 
 // Application dependencies
-#include <AP_SerialManager/AP_SerialManager.h>   // Serial manager library
 #include <AP_GPS/AP_GPS.h>             // ArduPilot GPS library
 #include <AP_Logger/AP_Logger.h>          // ArduPilot Mega Flash Memory Library
 #include <AP_Baro/AP_Baro.h>