diff --git a/src/vs/base/browser/ui/tree/objectTreeModel.ts b/src/vs/base/browser/ui/tree/objectTreeModel.ts
index f466b2534ce033afc7aafb12b0d68e5efd0fb048..6018c1221d8bfa5453585f515a610c6eae5a9d9c 100644
--- a/src/vs/base/browser/ui/tree/objectTreeModel.ts
+++ b/src/vs/base/browser/ui/tree/objectTreeModel.ts
@@ -41,7 +41,8 @@ export class ObjectTreeModel<T extends NonNullable<any>, TFilterData = void> imp
 
 	setChildren(
 		element: T | null,
-		children?: ISequence<ITreeElement<T>>,
+		// TODO@joao also use identity provider to preserve children when `children` is undefined!!!
+		children: ISequence<ITreeElement<T>> | undefined,
 		onDidCreateNode?: (node: ITreeNode<T, TFilterData>) => void,
 		onDidDeleteNode?: (node: ITreeNode<T, TFilterData>) => void
 	): Iterator<ITreeElement<T>> {
diff --git a/src/vs/base/test/browser/ui/tree/objectTreeModel.test.ts b/src/vs/base/test/browser/ui/tree/objectTreeModel.test.ts
index 7b7a3647a64a9d48948f2ec58116ae3fdadbf753..587441e1b4af90f8333ee671933784957bc15c66 100644
--- a/src/vs/base/test/browser/ui/tree/objectTreeModel.test.ts
+++ b/src/vs/base/test/browser/ui/tree/objectTreeModel.test.ts
@@ -53,7 +53,7 @@ suite('ObjectTreeModel', function () {
 		assert.deepEqual(toArray(list), [3, 4, 5]);
 		assert.equal(model.size, 3);
 
-		model.setChildren(null);
+		model.setChildren(null, Iterator.empty());
 		assert.deepEqual(toArray(list), []);
 		assert.equal(model.size, 0);
 	});
@@ -85,11 +85,11 @@ suite('ObjectTreeModel', function () {
 		assert.deepEqual(toArray(list), [0, 10, 11, 12, 120, 121, 1, 2]);
 		assert.equal(model.size, 8);
 
-		model.setChildren(0);
+		model.setChildren(0, Iterator.empty());
 		assert.deepEqual(toArray(list), [0, 1, 2]);
 		assert.equal(model.size, 3);
 
-		model.setChildren(null);
+		model.setChildren(null, Iterator.empty());
 		assert.deepEqual(toArray(list), []);
 		assert.equal(model.size, 0);
 	});