diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 9803ce2b..77dd4ad9 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -15,7 +15,7 @@ has 'print_z'           => (is => 'ro', required => 1); # Z used for printing in
 has 'height'            => (is => 'ro', required => 1); # layer height in unscaled coordinates
 
 # collection of expolygons generated by slicing the original geometry;
-# also known as 'islands' (all regions are merged here)
+# also known as 'islands' (all regions and surface types are merged here)
 has 'slices'            => (is => 'rw');
 
 # ordered collection of extrusion paths to fill surfaces for support material
@@ -78,14 +78,6 @@ sub region {
 # merge all regions' slices to get islands
 sub make_slices {
     my $self = shift;
-    
-    # optimization for single-region layers
-    my @regions_with_slices = grep { @{$_->slices} } @{$self->regions};
-    if (@regions_with_slices == 1) {
-        $self->slices([ map $_->expolygon, @{$regions_with_slices[0]->slices} ]);
-        return;
-    }
-    
     $self->slices(union_ex([ map $_->p, map @{$_->slices}, @{$self->regions} ]));
 }
 
diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index 825e928f..33cf6795 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -28,6 +28,7 @@ has 'overhang_width'    => (is => 'lazy');
 has 'lines' => (is => 'rw', default => sub { [] });
 
 # collection of surfaces generated by slicing the original geometry
+# divided by type top/bottom/internal
 has 'slices' => (is => 'rw', default => sub { [] });
 
 # collection of polygons or polylines representing thin walls contained 
@@ -266,8 +267,7 @@ sub make_perimeters {
                 $role = EXTR_ROLE_CONTOUR_INTERNAL_PERIMETER;
             }
             
-            ### Disable overhang detection for now
-            if (0 && $self->id > 0) {
+            if ($self->id > 0) {
                 # A perimeter is considered overhang if its centerline exceeds the lower layer slices
                 my $is_overhang = $is_contour
                     ? @{diff([$polygon], \@lower_slices)}