diff --git a/src/ng-select/items-list.ts b/src/ng-select/items-list.ts
index 8b320dbbf..150d7af6b 100644
--- a/src/ng-select/items-list.ts
+++ b/src/ng-select/items-list.ts
@@ -252,7 +252,7 @@ export class ItemsList {
 
     private _showSelectedItems(current: NgOption) {
         this._filteredItems.splice(current.index, 0, current);
-        if (isDefined(current.parent)) {
+        if (current.parent) {
             const parent = current.parent;
             const alreadyAdded = this._filteredItems.find(x => x === parent);
             if (!alreadyAdded) {
@@ -269,7 +269,7 @@ export class ItemsList {
 
     private _hideSelectedItems(current: NgOption) {
         this._filteredItems = this._filteredItems.filter(x => x !== current);
-        if (isDefined(current.parent)) {
+        if (current.parent) {
             const children = current.parent.children;
             const selectedChildrenCount = this._countItems(this.selectedItems, x => children.indexOf(x) > -1);
             if (children.length === selectedChildrenCount) {
diff --git a/src/ng-select/selection-model.ts b/src/ng-select/selection-model.ts
index a3bf2cda9..9f877ccd6 100644
--- a/src/ng-select/selection-model.ts
+++ b/src/ng-select/selection-model.ts
@@ -1,5 +1,4 @@
 import { NgOption } from './ng-select.types';
-import { isDefined } from './value-utils';
 
 export class SelectionModel {
     private _selected: NgOption[] = [];
@@ -12,7 +11,7 @@ export class SelectionModel {
         item.selected = true;
         this._selected.push(item);
         if (multiple) {
-            if (isDefined(item.parent)) {
+            if (item.parent) {
                 this._removeParent(item.parent);
                 const childrenCount = item.parent.children ? item.parent.children.length : 0;
                 const selectedCount = this._selected.filter(x => x.parent === item.parent).length;
@@ -29,7 +28,7 @@ export class SelectionModel {
         this._selected = this._selected.filter(x => x !== item);
         item.selected = false;
         if (multiple) {
-            if (isDefined(item.parent) && item.parent.selected) {
+            if (item.parent && item.parent.selected) {
                 const children = item.parent.children;
                 this._removeParent(item.parent);
                 this._removeSelectedChildren(children);