diff --git a/src/polygon/HerePolygonOverlayRenderer.ts b/src/polygon/HerePolygonOverlayRenderer.ts
index 5be32a7..492bfbd 100644
--- a/src/polygon/HerePolygonOverlayRenderer.ts
+++ b/src/polygon/HerePolygonOverlayRenderer.ts
@@ -9,7 +9,7 @@
  */
 import {
   AbstractPolygonOverlayRenderer,
-  densifyAndNormalize,
+  densifyPolygonRing,
   type PolygonEntity,
   type PolygonState,
 } from '@mapconductor/js-sdk-core';
@@ -98,7 +98,9 @@ function buildLineString(
   // Core pipeline: densify (great-circle when geodesic, linear lat/lng
   // otherwise — Android's straight-line semantics) and normalize into HERE's
   // [-180, 180] longitude range.
-  for (const point of densifyAndNormalize(points, geodesic)) {
+  // リングの閉じる辺（末尾 → 先頭）も他の辺と同じく補間する（輪郭と同じ線にする）。
+  const ring = densifyPolygonRing(points, geodesic).map((point) => point.normalize());
+  for (const point of ring) {
     lineString.pushPoint(toGeoCoordinates(point));
   }
   return lineString;