diff --git a/src/slic3r/GUI/GUI_ObjectManipulation.cpp b/src/slic3r/GUI/GUI_ObjectManipulation.cpp
index 1848ddda74..f763cc5a12 100644
--- a/src/slic3r/GUI/GUI_ObjectManipulation.cpp
+++ b/src/slic3r/GUI/GUI_ObjectManipulation.cpp
@@ -244,15 +244,13 @@ void ObjectManipulation::update_settings_value(const GLCanvas3D::Selection& sele
         if ((0 <= obj_idx) && (obj_idx < (int)wxGetApp().model_objects()->size()))
         {
             bool changed_box = false;
-            if ((m_cache.object_idx != obj_idx) || (m_cache.instance_idx != instance_idx))
+            if (!m_cache.instance.matches_object(obj_idx))
             {
-                m_cache.object_idx = obj_idx;
-                m_cache.instance_idx = instance_idx;
-                m_cache.instance_box_size = (*wxGetApp().model_objects())[obj_idx]->raw_mesh().bounding_box().size();
+                m_cache.instance.set(obj_idx, instance_idx, (*wxGetApp().model_objects())[obj_idx]->raw_mesh().bounding_box().size());
                 changed_box = true;
             }
-            if (changed_box || !m_cache.scale.isApprox(100.0 * m_new_scale) || !m_cache.rotation.isApprox(m_new_rotation))
-                m_new_size = volume->get_instance_transformation().get_matrix(true, true) * m_cache.instance_box_size;
+            if (changed_box || !m_cache.instance.matches_instance(instance_idx) || !m_cache.scale.isApprox(100.0 * m_new_scale))
+                m_new_size = volume->get_instance_transformation().get_matrix(true, true) * m_cache.instance.box_size;
         }
         else
             // this should never happen
@@ -270,8 +268,7 @@ void ObjectManipulation::update_settings_value(const GLCanvas3D::Selection& sele
     else if (selection.is_single_full_object())
     {
 #if ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
-        m_cache.object_idx = -1;
-        m_cache.instance_idx = -1;
+        m_cache.instance.reset();
 #endif // ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
 
         const BoundingBoxf3& box = selection.get_bounding_box();
@@ -286,8 +283,7 @@ void ObjectManipulation::update_settings_value(const GLCanvas3D::Selection& sele
     else if (selection.is_single_modifier() || selection.is_single_volume())
     {
 #if ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
-        m_cache.object_idx = -1;
-        m_cache.instance_idx = -1;
+        m_cache.instance.reset();
 #endif // ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
 
         // the selection contains a single volume
@@ -433,8 +429,7 @@ void ObjectManipulation::reset_settings_value()
     m_new_size = Vec3d::Zero();
     m_new_enabled = false;
 #if ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
-    m_cache.object_idx = -1;
-    m_cache.instance_idx = -1;
+    m_cache.instance.reset();
 #endif // ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
 #if !ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
     m_dirty = true;
@@ -514,6 +509,9 @@ void ObjectManipulation::change_scale_value(const Vec3d& scale)
     canvas->do_scale();
 
 #if ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
+    if (!m_cache.scale.isApprox(scale))
+        m_cache.instance.instance_idx = -1;
+
     m_cache.scale = scale;
 #endif // ENABLE_IMPROVED_SIDEBAR_OBJECTS_MANIPULATION
 }
diff --git a/src/slic3r/GUI/GUI_ObjectManipulation.hpp b/src/slic3r/GUI/GUI_ObjectManipulation.hpp
index ee768510ab..97cd2b6390 100644
--- a/src/slic3r/GUI/GUI_ObjectManipulation.hpp
+++ b/src/slic3r/GUI/GUI_ObjectManipulation.hpp
@@ -26,16 +26,25 @@ class ObjectManipulation : public OG_Settings
         std::string rotate_label_string;
         std::string scale_label_string;
 
-        int object_idx;
-        int instance_idx;
+        struct Instance
+        {
+            int object_idx;
+            int instance_idx;
+            Vec3d box_size;
 
-        Vec3d instance_box_size;
+            Instance() { reset(); }
+            void reset() { this->object_idx = -1; this->instance_idx = -1; this->box_size = Vec3d::Zero(); }
+            void set(int object_idx, int instance_idx, const Vec3d& box_size) { this->object_idx = object_idx; this->instance_idx = instance_idx; this->box_size = box_size; }
+            bool matches(int object_idx, int instance_idx) const { return (this->object_idx == object_idx) && (this->instance_idx == instance_idx); }
+            bool matches_object(int object_idx) const { return (this->object_idx == object_idx); }
+            bool matches_instance(int instance_idx) const { return (this->instance_idx == instance_idx); }
+        };
+
+        Instance instance;
 
         Cache() : position(Vec3d(DBL_MAX, DBL_MAX, DBL_MAX)) , rotation(Vec3d(DBL_MAX, DBL_MAX, DBL_MAX))
             , scale(Vec3d(DBL_MAX, DBL_MAX, DBL_MAX)) , size(Vec3d(DBL_MAX, DBL_MAX, DBL_MAX))
             , move_label_string("") , rotate_label_string("") , scale_label_string("")
-            , object_idx(-1)
-            , instance_idx(-1)
         {
         }
     };