diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index ef75ddb32..bc521cf1e 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -741,12 +741,11 @@ sub make_thumbnail {
         
         if ($Slic3r::have_threads) {
             Wx::PostEvent($self, Wx::PlThreadEvent->new(-1, $THUMBNAIL_DONE_EVENT, shared_clone([ $obj_idx, $thumbnail ])));
+            Slic3r::thread_cleanup();
             threads->exit;
         } else {
             $self->on_thumbnail_made($obj_idx);
         }
-        
-        Slic3r::thread_cleanup() if $Slic3r::have_threads;
     };
     
     @_ = ();
diff --git a/xs/xsp/ExPolygon.xsp b/xs/xsp/ExPolygon.xsp
index be8d4aa61..081b7ed25 100644
--- a/xs/xsp/ExPolygon.xsp
+++ b/xs/xsp/ExPolygon.xsp
@@ -29,12 +29,12 @@ ExPolygon::new(...)
 SV*
 ExPolygon::arrayref()
     CODE:
-        const unsigned int num_holes = THIS->holes.size();
         AV* av = newAV();
-        av_fill(av, num_holes);  // -1 +1
+        av_fill(av, THIS->holes.size());  // -1 +1
         av_store(av, 0, polygon2perl(THIS->contour));
-        for (unsigned int i = 0; i < num_holes; i++) {
-            av_store(av, i+1, polygon2perl(THIS->holes[i]));
+        int i = 0;
+        for (Polygons::iterator it = THIS->holes.begin(); it != THIS->holes.end(); ++it) {
+            av_store(av, ++i, polygon2perl(*it));
         }
         RETVAL = sv_bless(newRV_noinc((SV*)av), gv_stashpv("Slic3r::ExPolygon", GV_ADD));
     OUTPUT: