diff --git a/libraries/AP_Math/matrix3.h b/libraries/AP_Math/matrix3.h
index 4821e17f5c..3e74b807c5 100644
--- a/libraries/AP_Math/matrix3.h
+++ b/libraries/AP_Math/matrix3.h
@@ -38,6 +38,7 @@
 #pragma once
 
 #include "vector3.h"
+#include "vector2.h"
 
 // 3x3 matrix with elements of type T
 template <typename T>