diff --git a/libraries/AP_Arming/AP_Arming.cpp b/libraries/AP_Arming/AP_Arming.cpp
index 49a9bb9f50..f72c771e53 100644
--- a/libraries/AP_Arming/AP_Arming.cpp
+++ b/libraries/AP_Arming/AP_Arming.cpp
@@ -43,6 +43,7 @@
 #include <AP_VisualOdom/AP_VisualOdom.h>
 #include <AP_Parachute/AP_Parachute.h>
 #include <AP_OSD/AP_OSD.h>
+#include <AP_Relay/AP_Relay.h>
 #include <RC_Channel/RC_Channel.h>
 #include <AP_Button/AP_Button.h>
 #include <AP_FETtecOneWire/AP_FETtecOneWire.h>