diff --git a/src/ShapeUpgrade/ShapeUpgrade_UnifySameDomain.cxx b/src/ShapeUpgrade/ShapeUpgrade_UnifySameDomain.cxx
index f48c390f0f..73adb6eb41 100644
--- a/src/ShapeUpgrade/ShapeUpgrade_UnifySameDomain.cxx
+++ b/src/ShapeUpgrade/ShapeUpgrade_UnifySameDomain.cxx
@@ -2070,8 +2070,22 @@ Standard_Boolean ShapeUpgrade_UnifySameDomain::MergeSubSeq(const TopTools_Sequen
     TopoDS_Vertex V[2];
     V[0] = sae.FirstVertex(FE);
     V[1] = sae.LastVertex(TopoDS::Edge(theChain.Last()));
+    Standard_Boolean isClosed = V[0].IsSame(V[1]);
+    if (!isClosed)
+    {
+      // additionally check the points for equality to make a final decision about closedness of the result curve
+      gp_Pnt aP0 = BRep_Tool::Pnt(V[0]);
+      gp_Pnt aP1 = BRep_Tool::Pnt(V[1]);
+      Standard_Real aTol = Max(BRep_Tool::Tolerance(V[0]), BRep_Tool::Tolerance(V[1]));
+      if (aP0.SquareDistance(aP1) < aTol * aTol)
+      {
+        isClosed = Standard_True;
+        V[1] = V[0];
+        V[1].Reverse();
+      }
+    }
     TopoDS_Edge E;
-    if (V[0].IsSame(V[1])) {
+    if (isClosed) {
       // closed chain
       BRepAdaptor_Curve adef(FE);
       Handle(Geom_Circle) Cir1;
diff --git a/tests/bugs/heal/bug33028 b/tests/bugs/heal/bug33028
new file mode 100644
index 0000000000..4650b331ae
--- /dev/null
+++ b/tests/bugs/heal/bug33028
@@ -0,0 +1,36 @@
+puts "========================"
+puts " OCC33028: Standard_ConstructionError while using ShapeUpgrade_UnifySameDomain"
+puts "========================"
+puts ""
+
+stepread [locate_data_file bug33028_kalip.stp] s *
+
+set nbsBefore "
+Number of shapes in shape
+ VERTEX    : 543
+ EDGE      : 819
+ WIRE      : 359
+ FACE      : 289
+ SHELL     : 2
+ SOLID     : 2
+ COMPSOLID : 0
+ COMPOUND  : 1
+ SHAPE     : 2015
+"
+checknbshapes s_1 -ref ${nbsBefore} -t -m "result before attempt to simplify the model"
+
+unifysamedom result s_1
+
+set nbsAfter "
+Number of shapes in shape
+ VERTEX    : 515
+ EDGE      : 805
+ WIRE      : 359
+ FACE      : 289
+ SHELL     : 2
+ SOLID     : 2
+ COMPSOLID : 0
+ COMPOUND  : 1
+ SHAPE     : 1973
+"
+checknbshapes result -ref ${nbsAfter} -t -m "result after attempt to simplify the model"