diff --git a/lib/Slic3r/ExPolygon.pm b/lib/Slic3r/ExPolygon.pm
index 18789a747..0ef2d977a 100644
--- a/lib/Slic3r/ExPolygon.pm
+++ b/lib/Slic3r/ExPolygon.pm
@@ -5,7 +5,7 @@ use warnings;
 # an ExPolygon is a polygon with holes
 
 use Math::Geometry::Voronoi;
-use Slic3r::Geometry qw(point_in_polygon X Y A B);
+use Slic3r::Geometry qw(X Y A B point_in_polygon);
 use Slic3r::Geometry::Clipper qw(union_ex JT_MITER);
 
 # the constructor accepts an array of polygons 
diff --git a/lib/Slic3r/Geometry.pm b/lib/Slic3r/Geometry.pm
index f28db1507..599cde44a 100644
--- a/lib/Slic3r/Geometry.pm
+++ b/lib/Slic3r/Geometry.pm
@@ -19,7 +19,7 @@ our @EXPORT_OK = qw(
     polygon_remove_acute_vertices polygon_remove_parallel_continuous_edges
     shortest_path collinear scale unscale merge_collinear_lines
     rad2deg_dir bounding_box_center line_intersects_any douglas_peucker
-    polyline_remove_short_segments normal triangle_normal
+    polyline_remove_short_segments normal triangle_normal polygon_is_convex
 );
 
 use XXX;
@@ -295,6 +295,15 @@ sub polygon_has_vertex {
     return 0;
 }
 
+sub polygon_is_convex {
+    my ($points) = @_;
+    for (my $i = 0; $i <= $#$points; $i++) {
+        my $angle = angle3points($points->[$i-1], $points->[$i-2], $points->[$i]);
+        return 0 if $angle < PI;
+    }
+    return 1;
+}
+
 sub polyline_length {
     my ($polyline) = @_;
     my $length = 0;
diff --git a/t/geometry.t b/t/geometry.t
index bc81cb610..0ff61e375 100644
--- a/t/geometry.t
+++ b/t/geometry.t
@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 17;
+plan tests => 20;
 
 BEGIN {
     use FindBin;
@@ -12,7 +12,7 @@ BEGIN {
 use Slic3r;
 use Slic3r::Geometry qw(PI polyline_remove_parallel_continuous_edges 
     polyline_remove_acute_vertices polygon_remove_acute_vertices
-    polygon_remove_parallel_continuous_edges);
+    polygon_remove_parallel_continuous_edges polygon_is_convex);
 
 #==========================================================
 
@@ -143,4 +143,15 @@ is Slic3r::Geometry::can_connect_points(@$points, $polygons), 0, 'can_connect_po
     is scalar(@$polygon), 6, 'polyline_remove_acute_vertices';
 }
 
+#==========================================================
+
+{
+    my $cw_square = [ [0,0], [0,10], [10,10], [10,0] ];
+    is polygon_is_convex($cw_square), 0, 'cw square is not convex';
+    is polygon_is_convex([ reverse @$cw_square ]), 1, 'ccw square is convex';
+    
+    my $convex1 = [ [0,0], [10,0], [10,10], [0,10], [0,6], [4,6], [4,4], [0,4] ];
+    is polygon_is_convex($convex1), 0, 'concave polygon';
+}
+
 #==========================================================
\ No newline at end of file