diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index ead971c745..9c20da092d 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -416,8 +416,8 @@ sub clip_fill_surfaces {
     my $overhangs = [];  # arrayref of polygons
     for my $layer_id (reverse 0..$#{$self->layers}) {
         my $layer = $self->layers->[$layer_id];
-        my @layer_internal = ();
-        my @new_internal = ();
+        my @layer_internal = ();  # arrayref of Surface objects
+        my @new_internal = ();    # arrayref of Surface objects
         
         # clip this layer's internal surfaces to @overhangs
         foreach my $layerm (@{$layer->regions}) {
@@ -451,10 +451,10 @@ sub clip_fill_surfaces {
         if ($layer_id > 0) {
             my $solid = diff(
                 [ map @$_, @{$layer->slices} ],
-                \@layer_internal,
+                [ map $_->p, @layer_internal ],
             );
             $overhangs = offset($solid, +$additional_margin);
-            push @$overhangs, @new_internal;  # propagate upper overhangs
+            push @$overhangs, map $_->p, @new_internal;  # propagate upper overhangs
         }
     }
 }
diff --git a/t/fill.t b/t/fill.t
index 02b6a307cc..0a5a0a724a 100644
--- a/t/fill.t
+++ b/t/fill.t
@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 41;
+plan tests => 42;
 
 BEGIN {
     use FindBin;
@@ -187,6 +187,13 @@ for my $pattern (qw(rectilinear honeycomb hilbertcurve concentric)) {
     ok !(defined first { !$convex_hull->encloses_point($_) } @infill_points), "infill does not exceed perimeters ($pattern)";
 }
 
+{
+    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";
+}
+
 {
     my $config = Slic3r::Config->new_from_defaults;
     $config->set('skirts', 0);