diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 5e06e952a..6226f0555 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -332,8 +332,15 @@ sub process_bridges {
                 my $line_between_midpoints = Slic3r::Line->new(@midpoints);
                 $bridge_angle = rad2deg_dir($line_between_midpoints->direction);
             } elsif (@edges == 1) {
-                my $line = Slic3r::Line->new($edges[0]->[0], $edges[0]->[-1]);
-                $bridge_angle = rad2deg_dir($line->direction);
+                # TODO: this case includes both U-shaped bridges and plain overhangs;
+                # we need a trapezoidation algorithm to detect the actual bridged area
+                # and separate it from the overhang area.
+                # in the mean time, we're treating as overhangs all cases where
+                # our supporting edge is a straight line
+                if (@{$edges[0]} > 2) {
+                    my $line = Slic3r::Line->new($edges[0]->[0], $edges[0]->[-1]);
+                    $bridge_angle = rad2deg_dir($line->direction);
+                }
             } else {
                 my $center = bounding_box_center([ map @$_, @edges ]);
                 my $x = my $y = 0;
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 56b794baa..540c44d90 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -446,14 +446,38 @@ sub infill_every_layers {
 sub generate_support_material {
     my $self = shift;
     
+    # determine unsupported surfaces
+    my %layers = ();
+    my @unsupported_expolygons = ();
+    {
+        my (@a, @b) = ();
+        for (my $i = $#{$self->layers}; $i >=0; $i--) {
+            my $layer = $self->layers->[$i];
+            my @c = ();
+            if (@b) {
+                @c = @{diff_ex(
+                    [ map @$_, @b ],
+                    [ map @$_, map $_->expolygon->offset_ex(scale $Slic3r::flow_width), @{$layer->slices} ],
+                )};
+                $layers{$i} = [@c];
+            }
+            @b = @{union_ex([ map @$_, @c, @a ])};
+            
+            # get unsupported surfaces for current layer
+            @a = map $_->expolygon->offset_ex(scale $Slic3r::flow_spacing * $Slic3r::perimeters),
+                grep $_->surface_type eq 'bottom' && !defined $_->bridge_angle,
+                @{$layer->fill_surfaces};
+            
+            $_->simplify(scale $Slic3r::flow_spacing * 3) for @a;
+            push @unsupported_expolygons, @a;
+        }
+    }
+    return if !@unsupported_expolygons;
+    
     # generate paths for the pattern that we're going to use
     my $support_pattern = [];
     {
-        # get all surfaces needing support material
-        my @surfaces = grep $_->surface_type eq 'bottom' && !defined $_->bridge_angle,
-            map @{$_->slices}, grep $_->id > 0, @{$self->layers} or return;
-        
-        my @support_material_areas = @{union_ex([ map $_->p, @surfaces ])};
+        my @support_material_areas = @{union_ex([ map @$_, @unsupported_expolygons ])};
         
         for (1..$Slic3r::perimeters+1) {
             foreach my $expolygon (@support_material_areas) {
@@ -497,28 +521,6 @@ sub generate_support_material {
         );
     }
     
-    # now determine where to apply the pattern below unsupported surfaces
-    my %layers = ();
-    {
-        my (@a, @b) = ();
-        for (my $i = $#{$self->layers}; $i >=0; $i--) {
-            my $layer = $self->layers->[$i];
-            my @c = ();
-            if (@b) {
-                @c = @{diff_ex(
-                    [ map @$_, @b ],
-                    [ map @$_, map $_->expolygon->offset_ex(scale $Slic3r::flow_width), @{$layer->slices} ],
-                )};
-                $layers{$i} = [@c];
-            }
-            @b = @{union_ex([ map @$_, @c, @a ])};
-            @a = map $_->expolygon->offset_ex(scale 2),
-                grep $_->surface_type eq 'bottom' && !defined $_->bridge_angle,
-                @{$layer->slices};
-            $_->simplify(scale $Slic3r::flow_spacing * 3) for @a;
-        }
-    }
-    
     # apply the pattern to layers
     {
         my $clip_pattern = sub {
diff --git a/lib/Slic3r/Skein.pm b/lib/Slic3r/Skein.pm
index 71e5dce29..24b8685d1 100644
--- a/lib/Slic3r/Skein.pm
+++ b/lib/Slic3r/Skein.pm
@@ -114,15 +114,15 @@ sub go {
         }
     }
     
-    # free memory
-    @{$_->fill_surfaces} = () for @{$print->layers};
-    
     # generate support material
     if ($Slic3r::support_material) {
         $self->status_cb->(85, "Generating support material");
         $print->generate_support_material;
     }
     
+    # free memory (note that support material needs fill_surfaces)
+    @{$_->fill_surfaces} = () for @{$print->layers};
+    
     # make skirt
     $self->status_cb->(88, "Generating skirt");
     $print->extrude_skirt;