diff --git a/lib/Slic3r/Geometry/Clipper.pm b/lib/Slic3r/Geometry/Clipper.pm
index 4899d196..aeacab66 100644
--- a/lib/Slic3r/Geometry/Clipper.pm
+++ b/lib/Slic3r/Geometry/Clipper.pm
@@ -50,12 +50,15 @@ sub union_ex {
 }
 
 sub intersection_ex {
-    my ($subject, $clip) = @_;
-    
+    my ($subject, $clip, $jointype) = @_;
+    $jointype = PFT_NONZERO unless defined $jointype;
     $clipper->clear;
     $clipper->add_subject_polygons($subject);
     $clipper->add_clip_polygons($clip);
-    return $clipper->ex_execute(CT_INTERSECTION, PFT_NONZERO, PFT_NONZERO);
+    return [
+        map Slic3r::ExPolygon->new($_),
+            @{ $clipper->ex_execute(CT_INTERSECTION, $jointype, $jointype) },
+    ];
 }
 
 1;
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 82dfe585..2edf8c32 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -83,8 +83,8 @@ sub detect_surfaces_type {
     my $surface_difference = sub {
         my ($subject_surfaces, $clip_surfaces, $result_type) = @_;
         my $expolygons = diff_ex(
-            [ map { ref $_ eq 'ARRAY' ? $_ : $_->p } @$subject_surfaces ],
-            [ map { ref $_ eq 'ARRAY' ? $_ : $_->p } @$clip_surfaces ],
+            [ map { ref $_ eq 'ARRAY' ? $_ : ref $_ eq 'Slic3r::ExPolygon' ? @$_ : $_->p } @$subject_surfaces ],
+            [ map { ref $_ eq 'ARRAY' ? $_ : ref $_ eq 'Slic3r::ExPolygon' ? @$_ : $_->p } @$clip_surfaces ],
         );
         return grep $_->contour->is_printable,
             map Slic3r::Surface->cast_from_expolygon($_, surface_type => $result_type), 
@@ -171,6 +171,15 @@ sub detect_surfaces_type {
             $_->surface_type('bottom') for @bottom;
         }
         
+        # now, if the object contained a thin membrane, we could have overlapping bottom
+        # and top surfaces; let's do an intersection to discover them and consider them
+        # as bottom surfaces (to allow for bridge detection)
+        if (@top && @bottom) {
+            my $overlapping = intersection_ex([ map $_->p, @top ], [ map $_->p, @bottom ]);
+            Slic3r::debugf "  layer %d contains %d membrane(s)\n", $layer->id, scalar(@$overlapping);
+            @top = $surface_difference->([@top], $overlapping, 'top');
+        }
+        
         # find internal surfaces (difference between top/bottom surfaces and others)
         @internal = $surface_difference->($layer->surfaces, [@top, @bottom], 'internal');
         
@@ -353,7 +362,7 @@ sub infill_every_layers {
                                     map $_->p, grep $_->surface_type eq 'internal' && $_->depth_layers == $depth, 
                                         @$surfaces,
                                 ],
-                                safety_offset([ explode_expolygons($intersection) ]),
+                                safety_offset($intersection),
                             )};
                     }
                     @$surfaces = @new_surfaces;
@@ -374,7 +383,7 @@ sub infill_every_layers {
                                     map $_->p, grep $_->surface_type eq 'internal' && $_->depth_layers == $depth, 
                                         @$lower_surfaces,
                                 ],
-                                safety_offset([ explode_expolygons($intersection) ]),
+                                safety_offset($intersection),
                             )};
                     }
                     @$lower_surfaces = @new_surfaces;