diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index f977f5fd3..d43c9adf7 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1320,10 +1320,12 @@ void GLCanvas3D::Selection::add_all()
         return;
 
     m_mode = Instance;
+    clear();
 
     for (unsigned int i = 0; i < (unsigned int)m_volumes->size(); ++i)
     {
-        _add_volume(i);
+        if (!(*m_volumes)[i]->is_wipe_tower)
+            _add_volume(i);
     }
 
     _update_type();
@@ -1399,6 +1401,12 @@ bool GLCanvas3D::Selection::is_single_full_instance() const
     return false;
 }
 
+bool GLCanvas3D::Selection::is_from_single_object() const
+{
+    int idx = get_object_idx();
+    return (0 <= idx) && (idx < 1000);
+}
+
 int GLCanvas3D::Selection::get_object_idx() const
 {
     return (m_cache.content.size() == 1) ? m_cache.content.begin()->first : -1;
diff --git a/src/slic3r/GUI/GLCanvas3D.hpp b/src/slic3r/GUI/GLCanvas3D.hpp
index f5ae70919..5787a60e7 100644
--- a/src/slic3r/GUI/GLCanvas3D.hpp
+++ b/src/slic3r/GUI/GLCanvas3D.hpp
@@ -501,7 +501,7 @@ public:
         bool is_multiple_volume() const { return m_type == MultipleVolume; }
         bool is_mixed() const { return m_type == Mixed; }
         bool is_from_single_instance() const { return get_instance_idx() != -1; }
-        bool is_from_single_object() const { return get_object_idx() != -1; }
+        bool is_from_single_object() const;
 
         bool contains_volume(unsigned int volume_idx) const { return std::find(m_list.begin(), m_list.end(), volume_idx) != m_list.end(); }