diff --git a/src/slic3r/GUI/Camera.cpp b/src/slic3r/GUI/Camera.cpp
index 841a678ca7..341bfd4322 100644
--- a/src/slic3r/GUI/Camera.cpp
+++ b/src/slic3r/GUI/Camera.cpp
@@ -44,6 +44,8 @@ void Camera::set_type(EType type)
         m_type = type;
         if (m_update_config_on_type_change_enabled)
             wxGetApp().app_config->set("use_perspective_camera", (m_type == EType::Perspective) ? "1" : "0");
+
+        update_projection();
     }
 }
 
@@ -634,6 +636,37 @@ void Camera::update_zenit()
     m_zenit = Geometry::rad2deg(0.5 * M_PI - std::acos(std::clamp(-get_dir_forward().dot(Vec3d::UnitZ()), -1.0, 1.0)));
 }
 
+void Camera::update_projection()
+{
+    double w = 0.5 * (double)m_viewport[2];
+    double h = 0.5 * (double)m_viewport[3];
+
+    const double inv_zoom = get_inv_zoom();
+    w *= inv_zoom;
+    h *= inv_zoom;
+
+    switch (m_type)
+    {
+    default:
+    case EType::Ortho:
+    {
+        m_gui_scale = 1.0;
+        break;
+    }
+    case EType::Perspective:
+    {
+        // scale near plane to keep w and h constant on the plane at z = m_distance
+        const double scale = m_frustrum_zs.first / m_distance;
+        w *= scale;
+        h *= scale;
+        m_gui_scale = scale;
+        break;
+    }
+    }
+
+    apply_projection(-w, w, -h, h, m_frustrum_zs.first, m_frustrum_zs.second);
+}
+
 } // GUI
 } // Slic3r
 
diff --git a/src/slic3r/GUI/Camera.hpp b/src/slic3r/GUI/Camera.hpp
index 183086fe27..2729474d60 100644
--- a/src/slic3r/GUI/Camera.hpp
+++ b/src/slic3r/GUI/Camera.hpp
@@ -164,6 +164,7 @@ private:
     void set_default_orientation();
     Vec3d validate_target(const Vec3d& target) const;
     void update_zenit();
+    void update_projection();
 };
 
 } // GUI
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 39dde081a1..9533319ca2 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -7053,10 +7053,13 @@ Vec3d GLCanvas3D::_mouse_to_3d(const Point& mouse_pos, const float* z)
         return hit.is_valid() ? hit.position.cast<double>() : _mouse_to_bed_3d(mouse_pos);
     }
     else {
-        const Camera& camera = wxGetApp().plater()->get_camera();
+        Camera& camera = wxGetApp().plater()->get_camera();
+        const Camera::EType type = camera.get_type();
+        camera.set_type(Camera::EType::Ortho);
         const Vec4i viewport(camera.get_viewport().data());
         Vec3d out;
         igl::unproject(Vec3d(mouse_pos.x(), viewport[3] - mouse_pos.y(), *z), camera.get_view_matrix().matrix(), camera.get_projection_matrix().matrix(), viewport, out);
+        camera.set_type(type);
         return out;
     }
 }