diff --git a/src/db/db/dbDeepRegion.cc b/src/db/db/dbDeepRegion.cc
index 884250907..72317757b 100644
--- a/src/db/db/dbDeepRegion.cc
+++ b/src/db/db/dbDeepRegion.cc
@@ -352,11 +352,16 @@ flatten_layer (db::DeepLayer &deep_layer)
     db::Cell &top_cell = layout.cell (*layout.begin_top_down ());
 
     db::Shapes flat_shapes (layout.is_editable ());
+
     for (db::RecursiveShapeIterator iter (layout, top_cell, deep_layer.layer ()); !iter.at_end (); ++iter) {
       if (iter->is_polygon ()) {
         db::Polygon poly;
         iter->polygon (poly);
-        flat_shapes.insert (db::PolygonRef (poly.transformed (iter.trans ()), layout.shape_repository ()));
+        if (! iter->prop_id ()) {
+          flat_shapes.insert (db::PolygonRef (poly.transformed (iter.trans ()), layout.shape_repository ()));
+        } else {
+          flat_shapes.insert (db::PolygonRefWithProperties (db::PolygonRef (poly.transformed (iter.trans ()), layout.shape_repository ()), iter->prop_id ()));
+        }
       }
     }
 
diff --git a/src/db/unit_tests/dbDeepRegionTests.cc b/src/db/unit_tests/dbDeepRegionTests.cc
index 5e2de4973..6cf0658d5 100644
--- a/src/db/unit_tests/dbDeepRegionTests.cc
+++ b/src/db/unit_tests/dbDeepRegionTests.cc
@@ -2444,6 +2444,46 @@ TEST(44_SizeWithProperties)
   db::compare_layouts (_this, target, tl::testdata () + "/algo/deep_region_au44.gds");
 }
 
+TEST(45_FlattenWithProperties)
+{
+  db::Layout ly;
+  {
+    std::string fn (tl::testdata ());
+    fn += "/algo/deep_region_42.gds";
+    tl::InputStream stream (fn);
+    db::Reader reader (stream);
+    reader.read (ly);
+  }
+
+  db::cell_index_type top_cell_index = *ly.begin_top_down ();
+  db::Cell &top_cell = ly.cell (top_cell_index);
+
+  db::DeepShapeStore dss;
+
+  unsigned int l1 = ly.get_layer (db::LayerProperties (1, 0));
+  unsigned int l2 = ly.get_layer (db::LayerProperties (2, 0));
+
+  db::RecursiveShapeIterator si1 (ly, top_cell, l1);
+  si1.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
+  db::Region r1 (si1, dss);
+
+  db::RecursiveShapeIterator si2 (ly, top_cell, l2);
+  si2.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
+  db::Region r2 (si2, dss);
+
+  db::Layout target;
+  unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (1, 0)), r1);
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (2, 0)), r2);
+
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1.flatten ());
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2.flatten ());
+
+  CHECKPOINT();
+  db::compare_layouts (_this, target, tl::testdata () + "/algo/deep_region_au45.gds");
+}
+
 TEST(100_Integration)
 {
   db::Layout ly;
diff --git a/testdata/algo/deep_region_au45.gds b/testdata/algo/deep_region_au45.gds
new file mode 100644
index 000000000..659325c02
Binary files /dev/null and b/testdata/algo/deep_region_au45.gds differ