diff --git a/libraries/AP_NavEKF/AP_NavEKF_core_common.h b/libraries/AP_NavEKF/AP_NavEKF_core_common.h
index 0adbded311..4c0d6c19ef 100644
--- a/libraries/AP_NavEKF/AP_NavEKF_core_common.h
+++ b/libraries/AP_NavEKF/AP_NavEKF_core_common.h
@@ -18,6 +18,7 @@
 
 #include <stdint.h>
 #include <AP_Math/AP_Math.h>
+#include <AP_Math/vectorN.h>
 
 /*
   this declares a common parent class for AP_NavEKF2 and