diff --git a/src/slic3r/GUI/MeshUtils.cpp b/src/slic3r/GUI/MeshUtils.cpp
index 60ea6c856d..88a4f29728 100644
--- a/src/slic3r/GUI/MeshUtils.cpp
+++ b/src/slic3r/GUI/MeshUtils.cpp
@@ -465,14 +465,17 @@ bool MeshRaycaster::unproject_on_mesh(const Vec2d& mouse_pos, const Transform3d&
 
 
 
-bool MeshRaycaster::is_valid_intersection(Vec3d point, Vec3d direction, const Transform3d& trafo) const 
+bool MeshRaycaster::intersects_line(Vec3d point, Vec3d direction, const Transform3d& trafo) const 
 {
-    point = trafo.inverse() * point;
+    Transform3d trafo_inv = trafo.inverse();
+    Vec3d to = trafo_inv * (point + direction);
+    point = trafo_inv * point;
+    direction = (to-point).normalized();
 
     std::vector<AABBMesh::hit_result> hits      = m_emesh.query_ray_hits(point, direction);
     std::vector<AABBMesh::hit_result> neg_hits  = m_emesh.query_ray_hits(point, -direction);
 
-    return !hits.empty() && !neg_hits.empty();
+    return !hits.empty() || !neg_hits.empty();
 }
 
 
diff --git a/src/slic3r/GUI/MeshUtils.hpp b/src/slic3r/GUI/MeshUtils.hpp
index 3645ecc026..a7dd3d7f75 100644
--- a/src/slic3r/GUI/MeshUtils.hpp
+++ b/src/slic3r/GUI/MeshUtils.hpp
@@ -187,7 +187,9 @@ public:
     
     const AABBMesh &get_aabb_mesh() const { return m_emesh; }
 
-    bool is_valid_intersection(Vec3d point, Vec3d direction, const Transform3d& trafo) const;
+    // Given a point and direction in world coords, returns whether the respective line
+    // intersects the mesh if it is transformed into world by trafo.
+    bool intersects_line(Vec3d point, Vec3d direction, const Transform3d& trafo) const;
 
     // Given a vector of points in woorld coordinates, this returns vector
     // of indices of points that are visible (i.e. not cut by clipping plane