diff --git a/t/clean_polylines.t b/t/clean_polylines.t
index 17c4ad6abb..84acab55e1 100644
--- a/t/clean_polylines.t
+++ b/t/clean_polylines.t
@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 7;
+plan tests => 8;
 
 BEGIN {
     use FindBin;
@@ -79,6 +79,9 @@ use Slic3r;
     ok @simplified == 1, 'gear simplified to a single polygon';
     note sprintf "original points: %d\nnew points: %d", $num_points, scalar(@{$simplified[0]});
     ok @{$simplified[0]} < $num_points, 'gear was further simplified using Douglas-Peucker';
+    
+    my @simplified_ex = Slic3r::ExPolygon->new($polygon)->simplify(10);
+    is_deeply \@simplified_ex, [ \@simplified ], 'simplified polygon equals simplified expolygon';
 }
 
 {