diff --git a/lib/Slic3r/ExPolygon.pm b/lib/Slic3r/ExPolygon.pm
index e710b265f..526791657 100644
--- a/lib/Slic3r/ExPolygon.pm
+++ b/lib/Slic3r/ExPolygon.pm
@@ -253,6 +253,7 @@ sub medial_axis {
     Slic3r::Geometry::polyline_remove_parallel_continuous_edges($polyline);
     
     if (Slic3r::Geometry::same_point($polyline->[0], $polyline->[-1])) {
+        return undef if @$polyline == 2;
         return Slic3r::Polygon->new(@$polyline[0..$#$polyline-1]);
     } else {
         return Slic3r::Polyline->new($polyline);