diff --git a/src/libslic3r/QuadricEdgeCollapse.cpp b/src/libslic3r/QuadricEdgeCollapse.cpp
index 2e1b7089b..6609879cd 100644
--- a/src/libslic3r/QuadricEdgeCollapse.cpp
+++ b/src/libslic3r/QuadricEdgeCollapse.cpp
@@ -7,7 +7,10 @@
 
 using namespace Slic3r;
 
+// Faster debug, comment when you want deep check 
+#ifndef NDEBUG
 #define NDEBUG
+#endif // !NDEBUG
 
 // only private namespace not neccessary be in .hpp
 namespace QuadricEdgeCollapse {
@@ -105,10 +108,17 @@ namespace QuadricEdgeCollapse {
 #endif /* NDEBUG */
 
     // constants --> may be move to config
-    const int status_init_size = 10; // in percents
     const uint32_t check_cancel_period = 16; // how many edge to reduce before call throw_on_cancel
     const size_t max_triangle_count_for_one_vertex = 50;
-} // namespace QuadricEdgeCollapse
+    // change speed of progress bargraph
+    const int status_init_size = 10; // in percents
+    // parts of init size
+    const int status_normal_size = 25;
+    const int status_sum_quadric = 25;
+    const int status_set_offsets = 10;
+    const int status_calc_errors = 30;
+    const int status_create_refs = 10;
+    } // namespace QuadricEdgeCollapse
 
 using namespace QuadricEdgeCollapse;
 
@@ -395,13 +405,6 @@ SymMat QuadricEdgeCollapse::create_quadric(const Triangle &t,
 std::tuple<TriangleInfos, VertexInfos, EdgeInfos, Errors> 
 QuadricEdgeCollapse::init(const indexed_triangle_set &its, ThrowOnCancel& throw_on_cancel, StatusFn& status_fn)
 {
-    // change speed of progress bargraph
-    const int status_normal_size = 25;
-    const int status_sum_quadric = 25;
-    const int status_set_offsets = 10;
-    const int status_calc_errors = 30;
-    const int status_create_refs = 10;
-
     int status_offset = 0;
     TriangleInfos t_infos(its.indices.size());
     VertexInfos   v_infos(its.vertices.size());
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp
index b9e5d111b..f70e3f93e 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp
@@ -55,6 +55,7 @@ void GLGizmoSimplify::on_render_input_window(float x, float y, float bottom_limi
     create_gui_cfg();
     const Selection &selection = m_parent.get_selection();
     int object_idx = selection.get_object_idx();
+    if (!is_selected_object(&object_idx)) return;
     ModelObject *obj = wxGetApp().plater()->model().objects[object_idx];
     ModelVolume *act_volume = obj->volumes.front();
 
@@ -329,9 +330,9 @@ void GLGizmoSimplify::on_set_state()
 {
     // Closing gizmo. e.g. selecting another one
     if (GLGizmoBase::m_state == GLGizmoBase::Off) {
-
         // refuse outgoing during simlification
-        if (m_state != State::settings) {
+        // object is not selected when it is deleted(cancel and close gizmo)
+        if (m_state != State::settings && is_selected_object()) {
             GLGizmoBase::m_state = GLGizmoBase::On;
             auto notification_manager = wxGetApp().plater()->get_notification_manager();
             notification_manager->push_notification(
@@ -383,4 +384,20 @@ void GLGizmoSimplify::request_rerender() {
     });
 }
 
+bool GLGizmoSimplify::is_selected_object(int *object_idx)
+{
+    int index = (object_idx != nullptr) ? *object_idx :
+        m_parent.get_selection().get_object_idx();
+    // no selected object --> can appear after delete model
+    if (index < 0) {
+        switch (m_state) {
+        case State::settings: close(); break;
+        case State::canceling: break;
+        default: m_state = State::canceling;
+        }
+        return false;
+    }
+    return true;
+}
+
 } // namespace Slic3r::GUI
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp
index 0f5bd5991..856b6298d 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp
@@ -38,6 +38,7 @@ private:
     void set_its(indexed_triangle_set &its);
     void create_gui_cfg();
     void request_rerender();
+    bool is_selected_object(int *object_idx = nullptr);
 
     std::atomic_bool m_is_valid_result; // differ what to do in apply
     std::atomic_bool m_exist_preview;   // set when process end