diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index 5a13a6e42..87bb12298 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -416,6 +416,9 @@ sub rotate {
     
     my ($obj_idx, $object) = $self->selected_object;
     
+    # we need thumbnail to be computed before allowing rotation
+    return if !$object->thumbnail;
+    
     if (!defined $angle) {
         $angle = Wx::GetNumberFromUser("", "Enter the rotation angle:", "Rotate", $object->rotate, -364, 364, $self);
         return if !$angle || $angle == -1;
@@ -446,7 +449,7 @@ sub arrange {
     my $total_parts = sum(map $_->instances_count, @{$self->{objects}}) or return;
     my @size = ();
     for my $a (X,Y) {
-        $size[$a] = max(map $_->rotated_size->[$a], @{$self->{objects}});
+        $size[$a] = max(map $_->size->[$a], @{$self->{objects}});
     }
     
     eval {
@@ -756,7 +759,7 @@ sub recenter {
             my $obj = $_;
             map {
                 my $instance = $_;
-                $instance, [ map $instance->[$_] + $obj->rotated_size->[$_], X,Y ];
+                $instance, [ map $instance->[$_] + $obj->size->[$_], X,Y ];
             } @{$obj->instances};
         } @{$self->{objects}},
     ]);
@@ -1059,6 +1062,7 @@ has 'scale'                 => (is => 'rw', default => sub { 1 });
 has 'rotate'                => (is => 'rw', default => sub { 0 });
 has 'instances'             => (is => 'rw', default => sub { [] }); # upward Y axis
 has 'thumbnail'             => (is => 'rw');
+has 'thumbnail_scaling_factor' => (is => 'rw');
 
 # statistics
 has 'facets'                => (is => 'rw');
@@ -1111,6 +1115,7 @@ sub make_thumbnail {
     
     my @points = map [ @$_[X,Y] ], @{$self->model_object->mesh->vertices};
     my $convex_hull = Slic3r::Polygon->new(convex_hull(\@points));
+    $self->thumbnail_scaling_factor($params{scaling_factor});
     for (@$convex_hull) {
         @$_ = map $_ * $params{scaling_factor}, @$_;
     }
@@ -1132,6 +1137,8 @@ sub set_rotation {
     if ($self->thumbnail) {
         $self->thumbnail->rotate(Slic3r::Geometry::deg2rad($angle - $self->rotate));
         $self->thumbnail->align_to_origin;
+        my $z_size = $self->size->[Z];
+        $self->size([ (map $_ / $self->thumbnail_scaling_factor, @{$self->thumbnail->size}), $z_size ]);
     }
     $self->rotate($angle);
 }
@@ -1150,14 +1157,6 @@ sub set_scale {
     $self->scale($scale);
 }
 
-sub rotated_size {
-    my $self = shift;
-    
-    return Slic3r::Polygon->new([0,0], [$self->size->[X], 0], [@{$self->size}], [0, $self->size->[Y]])
-        ->rotate(Slic3r::Geometry::deg2rad($self->rotate))
-        ->size;
-}
-
 package Slic3r::GUI::Plater::ObjectInfoDialog;
 use Wx qw(:dialog :id :misc :sizer :systemsettings);
 use Wx::Event qw(EVT_BUTTON EVT_TEXT_ENTER);
diff --git a/lib/Slic3r/Geometry.pm b/lib/Slic3r/Geometry.pm
index c89faaf6f..c483fd6cc 100644
--- a/lib/Slic3r/Geometry.pm
+++ b/lib/Slic3r/Geometry.pm
@@ -20,7 +20,7 @@ our @EXPORT_OK = qw(
     shortest_path collinear scale unscale merge_collinear_lines
     rad2deg_dir bounding_box_center line_intersects_any douglas_peucker
     polyline_remove_short_segments normal triangle_normal polygon_is_convex
-    scaled_epsilon bounding_box_3D size_3D
+    scaled_epsilon bounding_box_3D size_3D size_2D
 );
 
 
@@ -689,6 +689,14 @@ sub bounding_box_center {
     );
 }
 
+sub size_2D {
+    my @bounding_box = bounding_box(@_);
+    return (
+        ($bounding_box[X2] - $bounding_box[X1]),
+        ($bounding_box[Y2] - $bounding_box[Y1]),
+    );
+}
+
 # bounding_box_intersect($d, @a, @b)
 #   Return true if the given bounding boxes @a and @b intersect
 #   in $d dimensions.  Used by line_intersection().
diff --git a/lib/Slic3r/Polyline.pm b/lib/Slic3r/Polyline.pm
index 8cdecf39f..692e8e3ba 100644
--- a/lib/Slic3r/Polyline.pm
+++ b/lib/Slic3r/Polyline.pm
@@ -126,9 +126,7 @@ sub bounding_box {
 
 sub size {
     my $self = shift;
-    
-    my @extents = $self->bounding_box;
-    return [$extents[X2] - $extents[X1], $extents[Y2] - $extents[Y1]];
+    return [ Slic3r::Geometry::size_2D($self) ];
 }
 
 sub align_to_origin {