diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index 9c20da09..785344d7 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -411,7 +411,7 @@ sub clip_fill_surfaces {
     # We only want infill under ceilings; this is almost like an
     # internal support material.
     
-    my $additional_margin = scale 3;
+    my $additional_margin = scale 3*0;
     
     my $overhangs = [];  # arrayref of polygons
     for my $layer_id (reverse 0..$#{$self->layers}) {
@@ -450,10 +450,11 @@ sub clip_fill_surfaces {
         # (thus we also consider perimeters)
         if ($layer_id > 0) {
             my $solid = diff(
-                [ map @$_, @{$layer->slices} ],
+                [ map $_->p, map @{$_->fill_surfaces}, @{$layer->regions} ],
                 [ map $_->p, @layer_internal ],
             );
             $overhangs = offset($solid, +$additional_margin);
+            
             push @$overhangs, map $_->p, @new_internal;  # propagate upper overhangs
         }
     }
diff --git a/lib/Slic3r/Test.pm b/lib/Slic3r/Test.pm
index 3b547482..b7ea6171 100644
--- a/lib/Slic3r/Test.pm
+++ b/lib/Slic3r/Test.pm
@@ -90,6 +90,13 @@ sub model {
         $facets = [
             [0,1,2],[0,3,1],[0,4,3],[5,6,7],[8,6,5],[2,9,0],[6,10,11],[12,13,14],[15,16,17],[18,16,15],[19,20,21],[22,23,24],[25,23,22],[26,23,25],[27,23,26],[28,23,27],[29,30,31],[29,32,30],[29,28,32],[33,28,29],[33,23,28],[21,23,33],[20,23,21],[34,35,36],[37,35,34],[38,35,37],[39,35,38],[40,35,39],[41,35,40],[42,35,41],[43,35,42],[44,35,43],[45,35,44],[46,35,45],[47,35,46],[48,35,47],[49,50,51],[52,48,47],[23,49,24],[53,54,55],[56,57,58],[59,57,56],[60,57,59],[61,57,60],[62,57,61],[63,57,62],[64,57,63],[65,57,64],[66,57,65],[13,57,66],[54,67,55],[68,69,70],[71,69,68],[72,69,71],[73,69,72],[74,69,73],[75,69,74],[76,69,75],[77,69,76],[67,69,77],[70,16,68],[70,17,16],[78,79,80],[81,79,78],[82,79,81],[83,79,82],[84,79,83],[85,79,84],[86,79,85],[87,79,86],[88,8,5],[11,7,6],[11,89,7],[11,9,89],[11,0,9],[55,90,53],[55,79,90],[55,80,79],[91,11,10],[92,69,12],[92,70,69],[34,93,37],[47,94,52],[47,95,94],[47,57,95],[47,58,57],[51,24,49],[21,35,19],[21,36,35],[14,92,12],[86,10,87],[86,91,10],[77,55,67],[66,14,13],[96,97,4],[98,99,100],[101,102,98],[103,101,98],[104,103,98],[105,106,107],[108,105,107],[109,108,107],[100,109,107],[110,111,112],[113,110,112],[114,115,116],[117,114,116],[118,119,120],[121,122,123],[124,121,123],[125,126,127],[128,129,130],[131,132,133],[71,131,133],[134,71,133],[135,134,133],[136,135,133],[137,138,139],[140,137,139],[141,140,139],[142,31,141],[142,141,139],[143,126,132],[144,145,146],[147,144,146],[127,147,146],[148,121,124],[149,148,124],[150,149,124],[151,150,124],[152,151,124],[153,152,124],[154,153,124],[155,154,124],[129,156,157],[130,129,157],[158,159,160],[161,158,160],[162,161,160],[163,162,160],[146,163,160],[164,165,166],[167,164,166],[168,169,170],[171,168,170],[139,171,170],[159,172,173],[123,174,142],[175,110,113],[173,175,113],[106,176,177],[178,106,177],[179,180,167],[112,179,167],[175,173,172],[119,118,181],[119,181,97],[119,97,96],[182,98,102],[182,102,183],[182,183,120],[182,120,119],[143,132,184],[184,185,143],[147,127,126],[174,123,122],[159,173,160],[126,125,133],[126,133,132],[186,187,188],[186,188,116],[186,116,115],[99,98,182],[109,100,99],[106,178,107],[114,117,177],[114,177,176],[128,130,187],[128,187,186],[135,136,157],[135,157,156],[163,146,145],[164,167,180],[179,112,111],[171,139,138],[189,155,166],[189,166,165],[149,150,93],[154,155,189],[31,142,174],[114,176,78],[81,78,176],[7,89,183],[89,9,120],[89,120,183],[78,80,114],[176,106,81],[88,5,103],[183,102,7],[118,120,9],[9,2,181],[9,181,118],[115,114,80],[82,81,106],[101,103,5],[102,101,5],[5,7,102],[97,181,2],[2,1,97],[1,3,97],[80,55,115],[172,159,59],[59,56,172],[3,4,97],[4,0,96],[105,108,82],[186,115,55],[82,106,105],[83,82,108],[60,59,159],[175,172,56],[119,96,0],[0,11,119],[108,109,84],[84,83,108],[55,77,186],[56,58,110],[56,110,175],[60,159,158],[11,91,182],[182,119,11],[91,86,182],[85,84,109],[86,85,99],[128,186,77],[58,111,110],[158,161,60],[26,25,137],[138,137,25],[99,182,86],[109,99,85],[77,76,128],[58,47,111],[61,60,161],[137,140,26],[27,26,140],[25,22,138],[129,128,76],[76,75,129],[75,74,129],[74,73,156],[73,72,135],[68,16,184],[68,184,132],[16,18,185],[161,162,62],[62,61,161],[179,111,47],[171,138,22],[156,129,74],[135,156,73],[134,135,72],[72,71,134],[68,132,131],[185,184,16],[18,15,185],[63,62,162],[28,27,140],[22,24,171],[71,68,131],[15,17,143],[15,143,185],[17,70,143],[70,92,126],[162,163,64],[64,63,162],[180,179,47],[47,46,180],[140,141,28],[168,171,24],[126,143,70],[92,14,147],[147,126,92],[14,66,144],[14,144,147],[65,64,163],[66,65,145],[46,45,180],[32,28,141],[24,51,168],[145,144,66],[163,145,65],[164,180,45],[45,44,164],[44,43,164],[43,42,165],[38,37,151],[150,151,37],[37,93,150],[141,31,30],[30,32,141],[169,168,51],[165,164,43],[189,165,42],[42,41,189],[40,39,152],[40,152,153],[151,152,39],[39,38,151],[93,34,149],[154,189,41],[153,154,41],[41,40,153],[148,149,34],[34,36,148],[36,21,121],[31,174,29],[121,148,36],[21,33,122],[21,122,121],[33,29,122],[174,122,29],[116,188,53],[104,98,10],[87,10,98],[98,100,87],[79,87,100],[79,100,107],[90,79,107],[90,107,178],[178,177,90],[53,90,177],[53,177,117],[117,116,53],[54,53,188],[54,188,187],[67,54,187],[67,187,130],[69,67,130],[69,130,157],[12,69,157],[12,157,136],[136,133,12],[12,133,125],[125,127,12],[13,12,127],[127,146,13],[57,13,146],[57,146,160],[95,57,160],[95,160,173],[173,113,95],[94,95,113],[113,112,94],[52,94,112],[48,52,112],[112,167,48],[35,48,167],[35,167,166],[19,35,166],[139,170,50],[50,49,139],[166,155,19],[20,19,155],[155,124,20],[23,20,124],[23,124,123],[49,23,123],[49,123,142],[142,139,49],[190,191,170],[192,191,190],[191,192,51],[191,51,50],[170,169,190],[169,51,192],[169,192,190],[170,191,50],[193,194,195],[196,197,198],[199,200,201],[198,202,203],[204,201,200],[205,204,200],[206,207,208],[206,208,205],[206,205,200],[207,206,209],[207,209,203],[207,203,202],[202,198,197],[197,196,210],[197,210,195],[197,195,194],[8,88,195],[8,195,210],[210,196,8],[196,198,8],[198,203,8],[203,209,8],[209,206,8],[206,200,8],[202,197,104],[207,202,104],[103,104,197],[103,197,194],[193,195,88],[88,103,194],[88,194,193],[200,199,8],[199,201,8],[204,205,6],[6,8,201],[6,201,204],[10,6,205],[10,205,208],[104,10,208],[104,208,207]
         ];
+    } elsif ($model_name eq 'pyramid') {
+        $vertices = [
+            [10,10,40],[0,0,0],[20,0,0],[20,20,0],[0,20,0],
+        ];
+        $facets = [
+            [0,1,2],[0,3,4],[3,1,4],[1,3,2],[3,0,2],[4,1,0],
+        ];
     } else {
         return undef;
     }
diff --git a/t/fill.t b/t/fill.t
index 0a5a0a72..67dd6be1 100644
--- a/t/fill.t
+++ b/t/fill.t
@@ -2,18 +2,18 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 42;
+plan tests => 43;
 
 BEGIN {
     use FindBin;
     use lib "$FindBin::Bin/../lib";
 }
 
-use List::Util qw(first);
+use List::Util qw(first sum);
 use Math::ConvexHull::MonotoneChain qw(convex_hull);
 use Slic3r;
-use Slic3r::Geometry qw(scale X Y);
-use Slic3r::Geometry::Clipper qw(union diff_ex);
+use Slic3r::Geometry qw(scale unscale X Y);
+use Slic3r::Geometry::Clipper qw(union diff_ex offset);
 use Slic3r::Surface qw(:types);
 use Slic3r::Test;
 
@@ -190,8 +190,47 @@ for my $pattern (qw(rectilinear honeycomb hilbertcurve concentric)) {
 {
     my $config = Slic3r::Config->new_from_defaults;
     $config->set('infill_only_where_needed', 1);
-    my $print = Slic3r::Test::init_print('20mm_cube', config => $config);
-    ok my $gcode = Slic3r::Test::gcode($print), "successful G-code generation when infill_only_where_needed is set";
+    $config->set('bottom_solid_layers', 0);
+    $config->set('infill_extruder', 2);
+    $config->set('infill_extrusion_width', 0.5);
+    $config->set('cooling', 0);                 # for preventing speeds from being altered
+    $config->set('first_layer_speed', '100%');  # for preventing speeds from being altered
+    
+    my $test = sub {
+        my $print = Slic3r::Test::init_print('pyramid', config => $config);
+        
+        my $tool = undef;
+        my @infill_extrusions = ();  # array of polylines
+        Slic3r::GCode::Reader->new->parse(Slic3r::Test::gcode($print), sub {
+            my ($self, $cmd, $args, $info) = @_;
+            
+            if ($cmd =~ /^T(\d+)/) {
+                $tool = $1;
+            } elsif ($cmd eq 'G1' && $info->{extruding} && $info->{dist_XY} > 0) {
+                if ($tool == $config->infill_extruder-1) {
+                    push @infill_extrusions, Slic3r::Line->new_scale(
+                        [ $self->X, $self->Y ],
+                        [ $info->{new_X}, $info->{new_Y} ],
+                    );
+                }
+            }
+        });
+        return 0 if !@infill_extrusions;  # prevent calling convex_hull() with no points
+        
+        my $convex_hull = Slic3r::Polygon->new(@{convex_hull([ map $_->pp, map @$_, @infill_extrusions ])});
+        
+        return unscale unscale sum(map $_->area, @{offset([$convex_hull], scale(+$config->infill_extrusion_width/2))});
+    };
+    
+    my $tolerance = 5;  # mm^2
+    
+    $config->set('solid_infill_below_area', 0);
+    ok $test->() < $tolerance,
+        'no infill is generated when using infill_only_where_needed on a pyramid';
+    
+    $config->set('solid_infill_below_area', 70);
+    ok abs($test->() - $config->solid_infill_below_area) < $tolerance,
+        'infill is only generated under the forced solid shells';
 }
 
 {