diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index 909288dd7..a23a85b6e 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -89,8 +89,12 @@ sub make_surfaces {
         foreach my $surface (@surfaces) {
             push @{$self->slices}, map Slic3r::Surface->new
                 (expolygon => $_, surface_type => S_TYPE_INTERNAL),
-                map $_->offset_ex(+$distance),
-                $surface->expolygon->offset_ex(-2*$distance);
+                @{union_ex([
+                    Slic3r::Geometry::Clipper::offset(
+                        [Slic3r::Geometry::Clipper::offset($surface->expolygon, -2*$distance)],
+                        +$distance,
+                    ),
+                ])};
         }
         
         # now detect thin walls by re-outgrowing offsetted surfaces and subtracting
@@ -187,14 +191,19 @@ sub make_perimeters {
             # offsetting a polygon can result in one or many offset polygons
             my @new_offsets = ();
             foreach my $expolygon (@last_offsets) {
-                my @offsets = map $_->offset_ex(+0.5*$distance), $expolygon->noncollapsing_offset_ex(-1.5*$distance);
+                my @offsets = @{union_ex([
+                    Slic3r::Geometry::Clipper::offset(
+                        [Slic3r::Geometry::Clipper::offset($expolygon, -1.5*$distance)], 
+                        +0.5*$distance,
+                    ),
+                ])};
                 push @new_offsets, @offsets;
                 
                 # where the above check collapses the expolygon, then there's no room for an inner loop
                 # and we can extract the gap for later processing
                 my $diff = diff_ex(
                     [ map @$_, $expolygon->offset_ex(-0.5*$distance) ],
-                    [ map @$_, map $_->offset_ex(+0.5*$distance), @offsets ],  # should these be offsetted in a single pass?
+                    [ Slic3r::Geometry::Clipper::offset([map @$_, @offsets], +0.5*$distance) ],
                 );
                 push @gaps, grep $_->area >= $gap_area_threshold, @$diff;
             }