diff --git a/src/db/db/dbPolygonTools.cc b/src/db/db/dbPolygonTools.cc
index 77f7c9dcd..e44ecfa8b 100644
--- a/src/db/db/dbPolygonTools.cc
+++ b/src/db/db/dbPolygonTools.cc
@@ -112,7 +112,7 @@ struct cut_polygon_edge
 {
   typedef typename PointType::coord_type coord_type;
   typedef typename db::edge<coord_type> edge_type;
-  typedef typename db::coord_traits<coord_type>::area_type projection_type;
+  typedef double projection_type;
 
   cut_polygon_edge ()
     : contour (-1), index (0), projected (0), point (), last_point ()
@@ -179,7 +179,7 @@ public:
 
   bool operator< (const loose_end_struct<CuttingEdgeType> &other) const
   {
-    if (proj () != other.proj ()) {
+    if (! db::coord_traits<double>::equal (proj (), other.proj ())) {
       return proj () < other.proj ();
     } else {
       return db::vprod_sign (edge (), other.edge ()) > 0;
@@ -196,13 +196,13 @@ static bool _cut_polygon_internal (const PolygonType &input, const Edge &line, C
   typedef db::edge<coord_type> edge_type;
   typedef cut_polygon_edge<point_type> cut_polygon_edge_type;
   typedef cut_polygon_segment<cut_polygon_edge_type> cutting_segment_type;
-  typedef typename db::coord_traits<coord_type>::area_type projection_type;
 
   bool do_hole_assignment = (input.holes () > 0);
   std::vector <PolygonType> hull_polygons;
   std::vector <PolygonType> hole_polygons;
 
   std::vector<cutting_segment_type> cutting_segments;
+  double line_length = line.double_length ();
 
   for (unsigned int nc = 0; nc < input.holes () + 1; ++nc) {
 
@@ -229,7 +229,7 @@ static bool _cut_polygon_internal (const PolygonType &input, const Edge &line, C
         int s1 = line.side_of (e.p1 ());
         int s2 = line.side_of (e.p2 ());
 
-        projection_type p = db::sprod (ip.second - line.p1 (), line.p2 () - line.p1 ());
+        double p = line_length * double (db::vprod (e.p1 () - line.p1 (), e.d ())) / double (db::vprod (line.d (), e.d ()));
 
         if (s1 < 0 && s2 >= 0) {
           // right -> left or on edge
diff --git a/src/db/unit_tests/dbGDS2Writer.cc b/src/db/unit_tests/dbGDS2Writer.cc
index 7c4f37358..0e0ebf893 100644
--- a/src/db/unit_tests/dbGDS2Writer.cc
+++ b/src/db/unit_tests/dbGDS2Writer.cc
@@ -1145,3 +1145,11 @@ TEST(121)
   opt.max_vertex_count = 4;
   run_test (_this, "t121.oas.gz", "t121_au.gds.gz", true, opt);
 }
+
+//  Extreme fracturing by max. points
+TEST(166)
+{
+  db::GDS2WriterOptions opt;
+  opt.max_vertex_count = 4;
+  run_test (_this, "t166.oas.gz", "t166_au.gds.gz", false, opt);
+}
diff --git a/src/db/unit_tests/dbPolygonTools.cc b/src/db/unit_tests/dbPolygonTools.cc
index 06224c533..6229f89f4 100644
--- a/src/db/unit_tests/dbPolygonTools.cc
+++ b/src/db/unit_tests/dbPolygonTools.cc
@@ -2241,3 +2241,20 @@ TEST(403)
     EXPECT_EQ (right_of.size (), size_t (0));
   }
 }
+
+//  issue 166
+TEST(404)
+{
+  db::Polygon poly;
+  std::string s ("(390,0;438,936;176,874;0,832;438,937;541,961;821,102)");
+  tl::Extractor ex (s.c_str ());
+  ex.read (poly);
+
+  std::vector<db::Polygon> sp;
+  db::split_polygon (poly, sp);
+  EXPECT_EQ (sp.size (), size_t (2));
+  if (sp.size () >= 2) {
+    EXPECT_EQ (sp[0].to_string (), "(390,0;438,936;390,925;438,937;541,961;821,102)");
+    EXPECT_EQ (sp[1].to_string (), "(0,832;176,874;390,925)");
+  }
+}
diff --git a/testdata/gds/t166.oas.gz b/testdata/gds/t166.oas.gz
new file mode 100644
index 000000000..3a209870a
Binary files /dev/null and b/testdata/gds/t166.oas.gz differ
diff --git a/testdata/gds/t166_au.gds.gz b/testdata/gds/t166_au.gds.gz
new file mode 100644
index 000000000..7766ef28e
Binary files /dev/null and b/testdata/gds/t166_au.gds.gz differ