diff --git a/examples/js/utils/BufferGeometryUtils.js b/examples/js/utils/BufferGeometryUtils.js
index ab1c2fabdc17d40618544ed48385b77ac9448c8c..f579a31f1bb6597d2c0f9590b8c9ddb029c15026 100644
--- a/examples/js/utils/BufferGeometryUtils.js
+++ b/examples/js/utils/BufferGeometryUtils.js
@@ -722,6 +722,7 @@ THREE.BufferGeometryUtils = {
 
 			var newGeometry = geometry.clone();
 			newGeometry.setIndex( newIndices );
+			newGeometry.clearGroups();
 
 			return newGeometry;
 
diff --git a/examples/jsm/utils/BufferGeometryUtils.js b/examples/jsm/utils/BufferGeometryUtils.js
index 030fa12e05a105a04d8a9bb18e50981d7bfd34c0..9d4cc8b0cecfee7eb618793e7536bad3948d29ee 100644
--- a/examples/jsm/utils/BufferGeometryUtils.js
+++ b/examples/jsm/utils/BufferGeometryUtils.js
@@ -734,6 +734,7 @@ var BufferGeometryUtils = {
 
 			var newGeometry = geometry.clone();
 			newGeometry.setIndex( newIndices );
+			newGeometry.clearGroups();
 
 			return newGeometry;