diff --git a/libraries/AP_SBusOut/AP_SBusOut.cpp b/libraries/AP_SBusOut/AP_SBusOut.cpp
index 7e6fc7b8c0..1c31191acf 100644
--- a/libraries/AP_SBusOut/AP_SBusOut.cpp
+++ b/libraries/AP_SBusOut/AP_SBusOut.cpp
@@ -38,6 +38,7 @@
  *
  */
 #include "AP_SBusOut.h"
+#include <AP_Math/AP_Math.h>
 #include <AP_SerialManager/AP_SerialManager.h>
 #include <SRV_Channel/SRV_Channel.h>
 
diff --git a/libraries/AP_SBusOut/AP_SBusOut.h b/libraries/AP_SBusOut/AP_SBusOut.h
index 84ca672c90..d108ec2cd4 100644
--- a/libraries/AP_SBusOut/AP_SBusOut.h
+++ b/libraries/AP_SBusOut/AP_SBusOut.h
@@ -8,7 +8,6 @@
 #pragma once
 
 #include <AP_HAL/AP_HAL.h>
-#include <AP_SerialManager/AP_SerialManager.h>
 #include <AP_Param/AP_Param.h>
 
 class AP_SBusOut {