diff --git a/src/db/unit_tests/dbDeepRegionTests.cc b/src/db/unit_tests/dbDeepRegionTests.cc
index 239d74313..0d4fd72de 100644
--- a/src/db/unit_tests/dbDeepRegionTests.cc
+++ b/src/db/unit_tests/dbDeepRegionTests.cc
@@ -2151,14 +2151,19 @@ TEST(40_BoolWithProperties)
   db::RecursiveShapeIterator si1 (ly, top_cell, l1);
   si1.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r1 (si1, dss);
+  EXPECT_EQ (r1.join_properties_on_merge (), true);
+  r1.set_join_properties_on_merge (false);
+  EXPECT_EQ (r1.join_properties_on_merge (), false);
 
   db::RecursiveShapeIterator si2 (ly, top_cell, l2);
   si2.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r2 (si2, dss);
+  r2.set_join_properties_on_merge (false);
 
   db::RecursiveShapeIterator si3 (ly, top_cell, l3);
   si3.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r3 (si3, dss);
+  r3.set_join_properties_on_merge (false);
 
   db::Layout target;
   unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
@@ -2169,6 +2174,9 @@ TEST(40_BoolWithProperties)
   target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (10, 0)), r1.merged ());
   target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (11, 0)), r2.merged ());
 
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (12, 0)), r1.merged (false, 0, true));
+  target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (13, 0)), r2.merged (false, 0, true));
+
   target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (20, 0)), r1 & r2);
   target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (21, 0)), r1.bool_and (r2, db::NoPropertyConstraint));
   target.insert (target_top_cell_index, target.get_layer (db::LayerProperties (22, 0)), r1.bool_and (r2, db::SamePropertiesConstraint));
@@ -2307,12 +2315,14 @@ TEST(42_DRCWithProperties)
   db::RecursiveShapeIterator si1 (ly, top_cell, l1);
   si1.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r1 (si1, dss);
+  r1.set_join_properties_on_merge (false);
   db::Region r1_nomerge (r1);
   r1_nomerge.set_merged_semantics (false);
 
   db::RecursiveShapeIterator si2 (ly, top_cell, l2);
   si2.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r2 (si2, dss);
+  r2.set_join_properties_on_merge (false);
   db::Region r2_nomerge (r2);
   r2_nomerge.set_merged_semantics (false);
 
@@ -2465,10 +2475,12 @@ TEST(44_SizeWithProperties)
   db::RecursiveShapeIterator si1 (ly, top_cell, l1);
   si1.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r1 (si1, dss);
+  r1.set_join_properties_on_merge (false);
 
   db::RecursiveShapeIterator si2 (ly, top_cell, l2);
   si2.apply_property_translator (db::PropertiesTranslator::make_pass_all ());
   db::Region r2 (si2, dss);
+  r2.set_join_properties_on_merge (false);
 
   db::Layout target;
   unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));
diff --git a/src/db/unit_tests/dbRegionTests.cc b/src/db/unit_tests/dbRegionTests.cc
index 6f1b1df49..da2c12249 100644
--- a/src/db/unit_tests/dbRegionTests.cc
+++ b/src/db/unit_tests/dbRegionTests.cc
@@ -2214,6 +2214,7 @@ TEST(52_PropertiesDeep)
   ++s;
   EXPECT_EQ (s.at_end (), true);
 
+  r.set_join_properties_on_merge (false);
   s = r.begin_merged ();
   EXPECT_EQ (s.at_end (), false);
   EXPECT_EQ (s.prop_id (), db::properties_id_type (0));
@@ -2234,6 +2235,16 @@ TEST(52_PropertiesDeep)
   ++s;
 
   EXPECT_EQ (s.at_end (), true);
+
+  r.set_join_properties_on_merge (true);
+  s = r.begin_merged ();
+  EXPECT_EQ (s.at_end (), false);
+
+  //  polygons are merged with "maximum" property value
+  EXPECT_EQ (db::PolygonWithProperties (*s, s.prop_id ()).to_string (), "(0,0;0,200;1,200;1,202;10,202;10,220;110,220;110,212;111,212;111,12;101,12;101,2;100,2;100,0) props={id=>42}");
+  ++s;
+
+  EXPECT_EQ (s.at_end (), true);
 }
 
 TEST(53_PropertiesDeepFromLayout)
@@ -2345,6 +2356,7 @@ TEST(53_PropertiesDeepFromLayout)
   ++s;
   EXPECT_EQ (s.at_end (), true);
 
+  r.set_join_properties_on_merge (false);
   s = r.begin_merged ();
   EXPECT_EQ (s.at_end (), false);
   EXPECT_EQ (s.prop_id (), db::properties_id_type (0));
@@ -2365,6 +2377,16 @@ TEST(53_PropertiesDeepFromLayout)
   ++s;
 
   EXPECT_EQ (s.at_end (), true);
+
+  r.set_join_properties_on_merge (true);
+  s = r.begin_merged ();
+  EXPECT_EQ (s.at_end (), false);
+
+  //  polygons are merged with "maximum" property value
+  EXPECT_EQ (db::PolygonWithProperties (*s, s.prop_id ()).to_string (), "(0,0;0,200;1,200;1,202;10,202;10,220;110,220;110,212;111,212;111,12;101,12;101,2;100,2;100,0) props={VALUE=>42}");
+  ++s;
+
+  EXPECT_EQ (s.at_end (), true);
 }
 
 TEST(54_PropertiesFilterDeep)
diff --git a/testdata/algo/deep_region_au40.gds b/testdata/algo/deep_region_au40.gds
index 84d6d4969..22a5519b0 100644
Binary files a/testdata/algo/deep_region_au40.gds and b/testdata/algo/deep_region_au40.gds differ
diff --git a/testdata/ruby/dbRegionTest.rb b/testdata/ruby/dbRegionTest.rb
index 88d7c8d4d..f5dc08881 100644
--- a/testdata/ruby/dbRegionTest.rb
+++ b/testdata/ruby/dbRegionTest.rb
@@ -1679,6 +1679,8 @@ class DBRegion_TestClass < TestBase
     iter = top.begin_shapes_rec(l1)
     iter.enable_properties()
     r = RBA::Region::new(iter, dss)
+    r.join_properties_on_merge = false
+    assert_equal(r.join_properties_on_merge, false)
 
     assert_equal(r.filtered(RBA::PolygonFilter::property_filter("one", 11)).to_s, "")
     assert_equal(r.filtered(RBA::PolygonFilter::property_filter("two", 17)).to_s, "")
@@ -1695,6 +1697,10 @@ class DBRegion_TestClass < TestBase
     rr.filter(RBA::PolygonFilter::property_filter("one", 17))
     assert_equal(csort(rr.to_s), csort("(1,1;1,201;101,201;101,1){one=>17}"))
 
+    r.join_properties_on_merge = true
+    assert_equal(r.join_properties_on_merge, true)
+    assert_equal(csort(r.filtered(RBA::PolygonFilter::property_filter("one", 42)).to_s), csort("(0,0;0,200;1,200;1,201;2,201;2,202;102,202;102,2;101,2;101,1;100,1;100,0){one=>42}"))
+
     dss._destroy
 
   end