diff --git a/src/db/db/dbAsIfFlatEdges.cc b/src/db/db/dbAsIfFlatEdges.cc
index 4e5e03581..e3d1edba8 100644
--- a/src/db/db/dbAsIfFlatEdges.cc
+++ b/src/db/db/dbAsIfFlatEdges.cc
@@ -450,7 +450,7 @@ AsIfFlatEdges::run_check (db::edge_relation_type rel, const Edges *other, db::Co
   }
 
   EdgeRelationFilter check (rel, d, metrics);
-  check.set_include_zero (other != 0);
+  check.set_include_zero (false);
   check.set_whole_edges (whole_edges);
   check.set_ignore_angle (ignore_angle);
   check.set_min_projection (min_projection);
diff --git a/src/db/db/dbAsIfFlatRegion.cc b/src/db/db/dbAsIfFlatRegion.cc
index e6cd117c1..7e31ca54a 100644
--- a/src/db/db/dbAsIfFlatRegion.cc
+++ b/src/db/db/dbAsIfFlatRegion.cc
@@ -642,7 +642,7 @@ AsIfFlatRegion::run_check (db::edge_relation_type rel, bool different_polygons,
   }
 
   EdgeRelationFilter check (rel, d, metrics);
-  check.set_include_zero (other != 0);
+  check.set_include_zero (false);
   check.set_whole_edges (whole_edges);
   check.set_ignore_angle (ignore_angle);
   check.set_min_projection (min_projection);
@@ -664,6 +664,7 @@ AsIfFlatRegion::run_single_polygon_check (db::edge_relation_type rel, db::Coord
   std::auto_ptr<FlatEdgePairs> result (new FlatEdgePairs ());
 
   EdgeRelationFilter check (rel, d, metrics);
+  check.set_include_zero (false);
   check.set_whole_edges (whole_edges);
   check.set_ignore_angle (ignore_angle);
   check.set_min_projection (min_projection);
diff --git a/src/db/db/dbDeepEdges.cc b/src/db/db/dbDeepEdges.cc
index e40c54898..081ac4c99 100644
--- a/src/db/db/dbDeepEdges.cc
+++ b/src/db/db/dbDeepEdges.cc
@@ -1404,6 +1404,7 @@ DeepEdges::run_check (db::edge_relation_type rel, const Edges *other, db::Coord
   ensure_merged_edges_valid ();
 
   EdgeRelationFilter check (rel, d, metrics);
+  check.set_include_zero (false);
   check.set_whole_edges (whole_edges);
   check.set_ignore_angle (ignore_angle);
   check.set_min_projection (min_projection);
diff --git a/src/db/db/dbDeepRegion.cc b/src/db/db/dbDeepRegion.cc
index 572e7a6ba..1d2cd5673 100644
--- a/src/db/db/dbDeepRegion.cc
+++ b/src/db/db/dbDeepRegion.cc
@@ -1466,6 +1466,7 @@ DeepRegion::run_check (db::edge_relation_type rel, bool different_polygons, cons
   ensure_merged_polygons_valid ();
 
   EdgeRelationFilter check (rel, d, metrics);
+  check.set_include_zero (false);
   check.set_whole_edges (whole_edges);
   check.set_ignore_angle (ignore_angle);
   check.set_min_projection (min_projection);
@@ -1494,6 +1495,7 @@ DeepRegion::run_single_polygon_check (db::edge_relation_type rel, db::Coord d, b
   ensure_merged_polygons_valid ();
 
   EdgeRelationFilter check (rel, d, metrics);
+  check.set_include_zero (false);
   check.set_whole_edges (whole_edges);
   check.set_ignore_angle (ignore_angle);
   check.set_min_projection (min_projection);
diff --git a/src/db/db/dbEdgePairRelations.cc b/src/db/db/dbEdgePairRelations.cc
index 2c60966bb..2ba777d99 100644
--- a/src/db/db/dbEdgePairRelations.cc
+++ b/src/db/db/dbEdgePairRelations.cc
@@ -66,6 +66,12 @@ bool euclidian_near_part_of_edge (bool include_zero, db::Coord d, const db::Edge
   db::Edge g (other);
   int s1 = e.side_of (g.p1 ());
   int s2 = e.side_of (g.p2 ());
+
+  //  "kissing corner" issue: force include zero if the edges are collinear and overlap.
+  if (! include_zero && s1 == 0 && s2 == 0 && e.intersect (g)) {
+    include_zero = true;
+  }
+
   int thr = include_zero ? 0 : -1;
 
   //  keep only part of other which is on the "inside" side of e
@@ -203,6 +209,12 @@ static bool var_near_part_of_edge (bool include_zero, db::Coord d, db::Coord dd,
   db::Edge g (other);
   int s1 = e.side_of (g.p1 ());
   int s2 = e.side_of (g.p2 ());
+
+  //  "kissing corner" issue: force include zero if the edges are collinear and overlap
+  if (! include_zero && s1 == 0 && s2 == 0 && e.intersect (g)) {
+    include_zero = true;
+  }
+
   int thr = include_zero ? 0 : -1;
 
   //  keep only part of other which is on the "inside" side of e
diff --git a/src/db/db/dbRegionUtils.cc b/src/db/db/dbRegionUtils.cc
index eb1114e1a..82a70313f 100644
--- a/src/db/db/dbRegionUtils.cc
+++ b/src/db/db/dbRegionUtils.cc
@@ -66,6 +66,21 @@ Edge2EdgeCheckBase::prepare_next_pass ()
   return false;
 }
 
+static inline bool shields (const db::EdgePair &ep, const db::Edge &q)
+{
+  db::Edge pe1 (ep.first ().p1 (), ep.second ().p2 ());
+  db::Edge pe2 (ep.second ().p1 (), ep.first ().p2 ());
+
+  std::pair<bool, db::Point> ip1 = pe1.intersect_point (q);
+  std::pair<bool, db::Point> ip2 = pe2.intersect_point (q);
+
+  if (ip1.first && ip2.first) {
+    return ip1.second != ip2.second || (ip1.second != q.p1 () && ip2.second != q.p2 ());
+  } else {
+    return false;
+  }
+}
+
 void
 Edge2EdgeCheckBase::add (const db::Edge *o1, size_t p1, const db::Edge *o2, size_t p2)
 {
@@ -128,8 +143,7 @@ Edge2EdgeCheckBase::add (const db::Edge *o1, size_t p1, const db::Edge *o2, size
       for (std::vector<size_t>::const_iterator i = nn.begin (); i != nn.end (); ++i) {
         if (! m_ep_discarded [*i]) {
           db::EdgePair ep = m_ep [*i].normalized ();
-          if (db::Edge (ep.first ().p1 (), ep.second ().p2 ()).intersect (*o2) &&
-              db::Edge (ep.second ().p1 (), ep.first ().p2 ()).intersect (*o2)) {
+          if (shields (ep, *o2)) {
             m_ep_discarded [*i] = true;
           }
         }
diff --git a/src/db/unit_tests/dbEdgePairRelations.cc b/src/db/unit_tests/dbEdgePairRelations.cc
index 2097e08ae..da7061089 100644
--- a/src/db/unit_tests/dbEdgePairRelations.cc
+++ b/src/db/unit_tests/dbEdgePairRelations.cc
@@ -346,7 +346,7 @@ TEST(7)
   res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 10)), db::Edge (db::Point (-1, 30), db::Point (-1, -20)), &output);
   EXPECT_EQ (res, false);
   f.set_include_zero (false);
-  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 10)), db::Edge (db::Point (0, 30), db::Point (0, -20)), &output);
+  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 10)), db::Edge (db::Point (0, 30), db::Point (0, 11)), &output);
   EXPECT_EQ (res, false);
   res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 10)), db::Edge (db::Point (1, 30), db::Point (1, -20)), &output);
   EXPECT_EQ (res, true);
@@ -355,3 +355,50 @@ TEST(7)
   EXPECT_EQ (res, false);
 }
 
+TEST(8_KissingCornerProblem)
+{
+  //  The kissing corner problem is solved by allowing distance-0 width and space relations and checking them
+  //  if the projection is >0.
+
+  db::EdgeRelationFilter f (db::WidthRelation, 10);
+  f.set_include_zero (false);
+  db::EdgePair output;
+  bool res;
+
+  f.set_metrics (db::Euclidian);
+  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 100)), db::Edge (db::Point (0, 201), db::Point (0, 101)), &output);
+  EXPECT_EQ (res, false);
+  res = f.check (db::Edge (db::Point (1, 0), db::Point (1, 100)), db::Edge (db::Point (0, 201), db::Point (0, 0)), &output);
+  EXPECT_EQ (res, false);
+  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 100)), db::Edge (db::Point (0, 200), db::Point (0, 100)), &output);
+  EXPECT_EQ (res, true);
+  EXPECT_EQ (output.first ().to_string () + ":" + output.second ().to_string (), "(0,90;0,100):(0,110;0,100)");
+  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 100)), db::Edge (db::Point (0, 200), db::Point (0, 50)), &output);
+  EXPECT_EQ (res, true);
+  EXPECT_EQ (output.first ().to_string () + ":" + output.second ().to_string (), "(0,40;0,100):(0,110;0,50)");
+  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 100)), db::Edge (db::Point (0, 0), db::Point (0, -100)), &output);
+  EXPECT_EQ (res, true);
+  EXPECT_EQ (output.first ().to_string () + ":" + output.second ().to_string (), "(0,0;0,10):(0,0;0,-10)");
+  res = f.check (db::Edge (db::Point (0, 0), db::Point (0, 100)), db::Edge (db::Point (0, -1), db::Point (0, -100)), &output);
+  EXPECT_EQ (res, false);
+
+  f = db::EdgeRelationFilter (db::SpaceRelation, 10);
+  f.set_include_zero (false);
+
+  f.set_metrics (db::Euclidian);
+  res = f.check (db::Edge (db::Point (0, 100), db::Point (0, 0)), db::Edge (db::Point (0, 101), db::Point (0, 201)), &output);
+  EXPECT_EQ (res, false);
+  res = f.check (db::Edge (db::Point (1, 100), db::Point (1, 0)), db::Edge (db::Point (0, 0), db::Point (0, 200)), &output);
+  EXPECT_EQ (res, false);
+  res = f.check (db::Edge (db::Point (0, 100), db::Point (0, 0)), db::Edge (db::Point (0, 100), db::Point (0, 200)), &output);
+  EXPECT_EQ (res, true);
+  EXPECT_EQ (output.first ().to_string () + ":" + output.second ().to_string (), "(0,100;0,90):(0,100;0,110)");
+  res = f.check (db::Edge (db::Point (0, 100), db::Point (0, 0)), db::Edge (db::Point (0, 50), db::Point (0, 200)), &output);
+  EXPECT_EQ (res, true);
+  EXPECT_EQ (output.first ().to_string () + ":" + output.second ().to_string (), "(0,100;0,40):(0,50;0,110)");
+  res = f.check (db::Edge (db::Point (0, 100), db::Point (0, 0)), db::Edge (db::Point (0, -100), db::Point (0, 0)), &output);
+  EXPECT_EQ (res, true);
+  EXPECT_EQ (output.first ().to_string () + ":" + output.second ().to_string (), "(0,10;0,0):(0,-10;0,0)");
+  res = f.check (db::Edge (db::Point (0, 100), db::Point (0, 0)), db::Edge (db::Point (0, -100), db::Point (0, -1)), &output);
+  EXPECT_EQ (res, false);
+}
diff --git a/src/db/unit_tests/dbEdges.cc b/src/db/unit_tests/dbEdges.cc
index 23e7fd371..1e4b27501 100644
--- a/src/db/unit_tests/dbEdges.cc
+++ b/src/db/unit_tests/dbEdges.cc
@@ -740,7 +740,7 @@ TEST(20)
     EXPECT_EQ (r1.has_valid_edges (), false);
     db::Edges r2 (db::RecursiveShapeIterator (ly, ly.cell (top), l2), false);
     EXPECT_EQ (r2.has_valid_edges (), false);
-    EXPECT_EQ (r1.separation_check (r2, 20).to_string (), "(50,0;50,30)/(40,40;40,10);(63,30;80,30)/(97,40;80,40);(80,30;80,20)/(80,40;80,50);(50,40;50,57)/(40,40;40,23);(80,70;80,40)/(80,40;80,70);(60,40;50,40)/(30,40;40,40)");
+    EXPECT_EQ (r1.separation_check (r2, 20).to_string (), "(50,0;50,30)/(40,40;40,10);(63,30;80,30)/(97,40;80,40);(50,40;50,57)/(40,40;40,23);(80,70;80,40)/(80,40;80,70)");
     EXPECT_EQ (r1.separation_check (r2, 20, false, db::Projection).to_string (), "(50,10;50,30)/(40,30;40,10);(80,70;80,40)/(80,40;80,70)");
     EXPECT_EQ (r1.separation_check (r2, 20, false, db::Euclidian, 90, 1).to_string (), "(50,0;50,30)/(40,40;40,10);(80,70;80,40)/(80,40;80,70)");
   }
diff --git a/src/drc/unit_tests/drcSimpleTests.cc b/src/drc/unit_tests/drcSimpleTests.cc
index c3a0a68c5..1a78bf780 100644
--- a/src/drc/unit_tests/drcSimpleTests.cc
+++ b/src/drc/unit_tests/drcSimpleTests.cc
@@ -533,3 +533,89 @@ TEST(12_NetlistJoinLabels)
   CHECKPOINT ();
   compare_netlists (_this, output, au);
 }
+
+TEST(13a_KissingCorners)
+{
+  std::string rs = tl::testsrc ();
+  rs += "/testdata/drc/drcSimpleTests_13a.drc";
+
+  std::string input = tl::testsrc ();
+  input += "/testdata/drc/kissing_corners.gds";
+
+  std::string au = tl::testsrc ();
+  au += "/testdata/drc/drcSimpleTests_au13a.gds";
+
+  std::string output = this->tmp_file ("tmp.gds");
+
+  {
+    //  Set some variables
+    lym::Macro config;
+    config.set_text (tl::sprintf (
+        "$drc_test_source = '%s'\n"
+        "$drc_test_target = '%s'\n"
+      , input, output)
+    );
+    config.set_interpreter (lym::Macro::Ruby);
+    EXPECT_EQ (config.run (), 0);
+  }
+
+  lym::Macro drc;
+  drc.load_from (rs);
+  EXPECT_EQ (drc.run (), 0);
+
+  //  verify
+
+  db::Layout layout;
+
+  {
+    tl::InputStream stream (output);
+    db::Reader reader (stream);
+    reader.read (layout);
+  }
+
+  CHECKPOINT ();
+  db::compare_layouts (_this, layout, au, db::NoNormalization);
+}
+
+TEST(13b_KissingCornersDeep)
+{
+  std::string rs = tl::testsrc ();
+  rs += "/testdata/drc/drcSimpleTests_13b.drc";
+
+  std::string input = tl::testsrc ();
+  input += "/testdata/drc/kissing_corners.gds";
+
+  std::string au = tl::testsrc ();
+  au += "/testdata/drc/drcSimpleTests_au13b.gds";
+
+  std::string output = this->tmp_file ("tmp.gds");
+
+  {
+    //  Set some variables
+    lym::Macro config;
+    config.set_text (tl::sprintf (
+        "$drc_test_source = '%s'\n"
+        "$drc_test_target = '%s'\n"
+      , input, output)
+    );
+    config.set_interpreter (lym::Macro::Ruby);
+    EXPECT_EQ (config.run (), 0);
+  }
+
+  lym::Macro drc;
+  drc.load_from (rs);
+  EXPECT_EQ (drc.run (), 0);
+
+  //  verify
+
+  db::Layout layout;
+
+  {
+    tl::InputStream stream (output);
+    db::Reader reader (stream);
+    reader.read (layout);
+  }
+
+  CHECKPOINT ();
+  db::compare_layouts (_this, layout, au, db::NoNormalization);
+}
diff --git a/testdata/drc/drcSimpleTests_13a.drc b/testdata/drc/drcSimpleTests_13a.drc
new file mode 100644
index 000000000..4f1d62ed0
--- /dev/null
+++ b/testdata/drc/drcSimpleTests_13a.drc
@@ -0,0 +1,17 @@
+source($drc_test_source)
+target($drc_test_target, "TOP")
+
+l1 = input(1, 0)
+l2 = input(2, 0)
+l3 = input(3, 0)
+
+l1.output(1, 0)
+l2.output(2, 0)
+l3.output(3, 0)
+
+l1.width(100.nm).output(100, 0)
+l1.space(100.nm).output(101, 0)
+l1.notch(100.nm).output(102, 0)
+l2.separation(l3, 100.nm).output(103, 0)
+l2.overlap(l3, 100.nm).output(104, 0)
+  
diff --git a/testdata/drc/drcSimpleTests_13b.drc b/testdata/drc/drcSimpleTests_13b.drc
new file mode 100644
index 000000000..5dcc56571
--- /dev/null
+++ b/testdata/drc/drcSimpleTests_13b.drc
@@ -0,0 +1,19 @@
+source($drc_test_source)
+target($drc_test_target, "TOP")
+
+deep
+
+l1 = input(1, 0)
+l2 = input(2, 0)
+l3 = input(3, 0)
+
+l1.output(1, 0)
+l2.output(2, 0)
+l3.output(3, 0)
+
+l1.width(100.nm).output(100, 0)
+l1.space(100.nm).output(101, 0)
+l1.notch(100.nm).output(102, 0)
+l2.separation(l3, 100.nm).output(103, 0)
+l2.overlap(l3, 100.nm).output(104, 0)
+  
diff --git a/testdata/drc/drcSimpleTests_au13a.gds b/testdata/drc/drcSimpleTests_au13a.gds
new file mode 100644
index 000000000..0e7e5b8c4
Binary files /dev/null and b/testdata/drc/drcSimpleTests_au13a.gds differ
diff --git a/testdata/drc/drcSimpleTests_au13b.gds b/testdata/drc/drcSimpleTests_au13b.gds
new file mode 100644
index 000000000..0e7e5b8c4
Binary files /dev/null and b/testdata/drc/drcSimpleTests_au13b.gds differ
diff --git a/testdata/drc/drcSuiteTests_au6.oas b/testdata/drc/drcSuiteTests_au6.oas
index bf5fabfd9..022252773 100644
Binary files a/testdata/drc/drcSuiteTests_au6.oas and b/testdata/drc/drcSuiteTests_au6.oas differ
diff --git a/testdata/drc/kissing_corners.gds b/testdata/drc/kissing_corners.gds
new file mode 100644
index 000000000..af4b474ff
Binary files /dev/null and b/testdata/drc/kissing_corners.gds differ