diff --git a/src/db/db/dbFillTool.cc b/src/db/db/dbFillTool.cc
index 5c38bbf40..ce9126e21 100644
--- a/src/db/db/dbFillTool.cc
+++ b/src/db/db/dbFillTool.cc
@@ -383,15 +383,15 @@ rasterize_extended (const db::Polygon &fp, const db::Box &fc_bbox, db::AreaMap &
 }
 
 static db::IMatrix2d
-compute_shear_matrix (const db::Vector &row_step, const db::Vector &column_step)
+compute_shear_matrix (const db::Vector &r, const db::Vector &c)
 {
-  db::IMatrix2d mr = db::IMatrix2d (1.0, 0.0, -double (row_step.y ()) / double (row_step.x ()), 1.0);
+  double det = r.x () * c.y () - r.y () * c.x ();
 
-  double csy = column_step.y () + mr.m21 () * column_step.x ();
+  double m11 = c.y () * r.x () / det;
+  double m12 = -c.x () * r.x () / det;
+  double m22 = c.y () * r.x () / det;
 
-  db::IMatrix2d mc = db::IMatrix2d (1.0, -double (column_step.x ()) / csy, 0.0, 1.0);
-
-  return mc * mr;
+  return IMatrix2d (m11, m12, m12, m22);
 }
 
 DB_PUBLIC bool
diff --git a/src/db/unit_tests/dbFillToolTests.cc b/src/db/unit_tests/dbFillToolTests.cc
index fbc6940a3..de3fa628b 100644
--- a/src/db/unit_tests/dbFillToolTests.cc
+++ b/src/db/unit_tests/dbFillToolTests.cc
@@ -52,3 +52,66 @@ TEST(1)
   db::compare_layouts (_this, ly, tl::testsrc () + "/testdata/algo/fill_tool_au1.gds");
 }
 
+TEST(2)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testsrc ());
+    fn += "/testdata/algo/fill_tool2.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type fill_cell = ly.cell_by_name ("FILL_CELL").second;
+  db::cell_index_type top_cell = ly.cell_by_name ("TOP").second;
+  unsigned int fill_layer = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region fill_region (db::RecursiveShapeIterator (ly, ly.cell (top_cell), fill_layer));
+
+  db::Region remaining_parts, remaining_polygons;
+
+  db::fill_region (&ly.cell (top_cell), fill_region, fill_cell, ly.cell (fill_cell).bbox (), db::Point (), true, &remaining_parts, db::Vector (50, 100), &remaining_polygons);
+
+  unsigned int l100 = ly.insert_layer (db::LayerProperties (100, 0));
+  unsigned int l101 = ly.insert_layer (db::LayerProperties (101, 0));
+  remaining_parts.insert_into (&ly, top_cell, l100);
+  remaining_polygons.insert_into (&ly, top_cell, l101);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, ly, tl::testsrc () + "/testdata/algo/fill_tool_au2.gds");
+}
+
+TEST(3)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testsrc ());
+    fn += "/testdata/algo/fill_tool3.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type fill_cell = ly.cell_by_name ("FILL_CELL").second;
+  db::cell_index_type top_cell = ly.cell_by_name ("TOP").second;
+  unsigned int fill_layer = ly.get_layer (db::LayerProperties (1, 0));
+
+  db::Region fill_region (db::RecursiveShapeIterator (ly, ly.cell (top_cell), fill_layer));
+
+  db::Region remaining_parts, remaining_polygons;
+
+  db::Vector ko (-100, -130);
+  db::Vector rs (230, 40);
+  db::Vector cs (40, 230);
+  db::fill_region (&ly.cell (top_cell), fill_region, fill_cell, ko, rs, cs, db::Point (), true, &remaining_parts, db::Vector (50, 100), &remaining_polygons);
+
+  unsigned int l100 = ly.insert_layer (db::LayerProperties (100, 0));
+  unsigned int l101 = ly.insert_layer (db::LayerProperties (101, 0));
+  remaining_parts.insert_into (&ly, top_cell, l100);
+  remaining_polygons.insert_into (&ly, top_cell, l101);
+
+  CHECKPOINT();
+  db::compare_layouts (_this, ly, tl::testsrc () + "/testdata/algo/fill_tool_au3.gds");
+}
+
diff --git a/testdata/algo/fill_tool1.gds b/testdata/algo/fill_tool1.gds
index 540163aa2..0bcaec0c4 100644
Binary files a/testdata/algo/fill_tool1.gds and b/testdata/algo/fill_tool1.gds differ
diff --git a/testdata/algo/fill_tool2.gds b/testdata/algo/fill_tool2.gds
new file mode 100644
index 000000000..c2e221473
Binary files /dev/null and b/testdata/algo/fill_tool2.gds differ
diff --git a/testdata/algo/fill_tool3.gds b/testdata/algo/fill_tool3.gds
new file mode 100644
index 000000000..d2470efa0
Binary files /dev/null and b/testdata/algo/fill_tool3.gds differ
diff --git a/testdata/algo/fill_tool_au1.gds b/testdata/algo/fill_tool_au1.gds
new file mode 100644
index 000000000..1cd62ae2c
Binary files /dev/null and b/testdata/algo/fill_tool_au1.gds differ
diff --git a/testdata/algo/fill_tool_au2.gds b/testdata/algo/fill_tool_au2.gds
new file mode 100644
index 000000000..a28cfd4c1
Binary files /dev/null and b/testdata/algo/fill_tool_au2.gds differ
diff --git a/testdata/algo/fill_tool_au3.gds b/testdata/algo/fill_tool_au3.gds
new file mode 100644
index 000000000..3d351b309
Binary files /dev/null and b/testdata/algo/fill_tool_au3.gds differ