diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index c83a5a038..fad99f6fe 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -4106,10 +4106,16 @@ void GLCanvas3D::on_mouse(wxMouseEvent& evt)
 #if ENABLE_EXTENDED_SELECTION
                 if (evt.LeftDown() && (m_hover_volume_id != -1))
                 {
-                    if (!evt.ShiftDown() || !m_selection.contains_volume(m_hover_volume_id))
-                        m_selection.add(m_hover_volume_id, !evt.ShiftDown());
-                    else
+                    bool already_selected = m_selection.contains_volume(m_hover_volume_id);
+                    bool shift_down = evt.ShiftDown();
+
+                    if (already_selected && shift_down)
                         m_selection.remove(m_hover_volume_id);
+                    else
+                    {
+                        bool add_as_single = !already_selected && !evt.ShiftDown();
+                        m_selection.add(m_hover_volume_id, add_as_single);
+                    }
 
                     m_gizmos.update_on_off_state(m_selection);
                     update_gizmos_data();
@@ -4229,8 +4235,8 @@ void GLCanvas3D::on_mouse(wxMouseEvent& evt)
         float z0 = 0.0f;
         float z1 = 1.0f;
 #if ENABLE_EXTENDED_SELECTION
-        // we do not want to translate objects if the user just clicked on an object while pressing shift (to add/remove it from the selection) and then drag
-        Vec3d cur_pos = evt.ShiftDown() ? m_mouse.drag.start_position_3D : Linef3(_mouse_to_3d(pos, &z0), _mouse_to_3d(pos, &z1)).intersect_plane(m_mouse.drag.start_position_3D(2));
+        // we do not want to translate objects if the user just clicked on an object while pressing shift to remove it from the selection and then drag
+        Vec3d cur_pos = m_selection.contains_volume(m_hover_volume_id) ? Linef3(_mouse_to_3d(pos, &z0), _mouse_to_3d(pos, &z1)).intersect_plane(m_mouse.drag.start_position_3D(2)) : m_mouse.drag.start_position_3D;
 #else
         Vec3d cur_pos = Linef3(_mouse_to_3d(pos, &z0), _mouse_to_3d(pos, &z1)).intersect_plane(m_mouse.drag.start_position_3D(2));
 #endif // ENABLE_EXTENDED_SELECTION
diff --git a/src/slic3r/GUI/GLGizmo.cpp b/src/slic3r/GUI/GLGizmo.cpp
index e190b1b3a..6965d95b7 100644
--- a/src/slic3r/GUI/GLGizmo.cpp
+++ b/src/slic3r/GUI/GLGizmo.cpp
@@ -1531,13 +1531,13 @@ void GLGizmoFlatten::on_render(const BoundingBoxf3& box) const
     // does not work correctly when there are multiple copies.
     Vec3d dragged_offset(Vec3d::Zero());
 #if ENABLE_EXTENDED_SELECTION
-        if (m_starting_center == Vec3d::Zero())
-            m_starting_center = selection.get_bounding_box().center();
-        dragged_offset = selection.get_bounding_box().center() - m_starting_center;
+    if (m_starting_center == Vec3d::Zero())
+        m_starting_center = selection.get_bounding_box().center();
+    dragged_offset = selection.get_bounding_box().center() - m_starting_center;
 #else
-        if (m_starting_center == Vec3d::Zero())
-            m_starting_center = box.center();
-        dragged_offset(box.center() - m_starting_center); 
+    if (m_starting_center == Vec3d::Zero())
+        m_starting_center = box.center();
+    dragged_offset = box.center() - m_starting_center; 
 #endif // ENABLE_EXTENDED_SELECTION   
 
     ::glEnable(GL_BLEND);
diff --git a/src/slic3r/GUI/GLGizmo.hpp b/src/slic3r/GUI/GLGizmo.hpp
index 14eac77e7..838c7b787 100644
--- a/src/slic3r/GUI/GLGizmo.hpp
+++ b/src/slic3r/GUI/GLGizmo.hpp
@@ -342,8 +342,6 @@ protected:
     virtual void on_start_dragging(const GLCanvas3D::Selection& selection);
 #else
     virtual void on_start_dragging(const BoundingBoxf3& box);
-    virtual void on_stop_dragging() { m_show_starting_box = false; }
-
 #endif // ENABLE_EXTENDED_SELECTION
     virtual void on_update(const Linef3& mouse_ray, const Point* mouse_pos);
 #if ENABLE_GIZMOS_RESET