diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 78ef1c9b85..b924e1902a 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -171,6 +171,7 @@ sub make_surfaces {
         my $diff = diff_ex(
             [ map $_->p, @surfaces ],
             $outgrown,
+            1,
         );
         
         push @{$self->thin_walls},
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 54dd602fca..97eb0a399e 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -330,7 +330,7 @@ sub extrude_skirt {
     my $skirt_height = $Slic3r::skirt_height;
     $skirt_height = $self->layer_count if $skirt_height > $self->layer_count;
     my @layers = map $self->layer($_), 0..($skirt_height-1);
-    my @points = map @$_, map $_->p, map @{ $_->slices }, @layers;
+    my @points = map @$_, map $_->p, map +(@{$_->slices}, @{$_->thin_walls}), @layers;
     return if !@points;
     
     # find out convex hull