diff --git a/libraries/AP_Math/vector2.cpp b/libraries/AP_Math/vector2.cpp
index ad0c7fd955..bec3dfdca9 100644
--- a/libraries/AP_Math/vector2.cpp
+++ b/libraries/AP_Math/vector2.cpp
@@ -437,6 +437,7 @@ template float Vector2<float>::angle(const Vector2<float> &v) const;
 template float Vector2<float>::angle(void) const;
 template bool Vector2<float>::segment_intersection(const Vector2<float>& seg1_start, const Vector2<float>& seg1_end, const Vector2<float>& seg2_start, const Vector2<float>& seg2_end, Vector2<float>& intersection);
 template bool Vector2<float>::circle_segment_intersection(const Vector2<float>& seg_start, const Vector2<float>& seg_end, const Vector2<float>& circle_center, float radius, Vector2<float>& intersection);
+template Vector2<float> Vector2<float>::perpendicular(const Vector2<float> &pos_delta, const Vector2<float> &v1);
 template Vector2<float> Vector2<float>::closest_point(const Vector2<float> &p, const Vector2<float> &v, const Vector2<float> &w);
 template float Vector2<float>::closest_distance_between_radial_and_point_squared(const Vector2<float> &w, const Vector2<float> &p);
 template float Vector2<float>::closest_distance_between_radial_and_point(const Vector2<float> &w, const Vector2<float> &p);