diff --git a/src/notebook.manager.ts b/src/notebook.manager.ts
index 24cf1ec..e2165f9 100644
--- a/src/notebook.manager.ts
+++ b/src/notebook.manager.ts
@@ -203,6 +203,9 @@ export class NotebookManager implements INotebookManager {
         // add a notebook to the favorites stored in global state
         let collectionNotebooks: Notebook[] = 
           notebookTreeDataProvider.context.globalState.get(notebookCollectionKey);
+        if (collectionNotebooks === undefined) {
+          collectionNotebooks = [];
+        }
         collectionNotebooks.push(notebook);
         notebookTreeDataProvider.context.globalState.update(notebookCollectionKey, collectionNotebooks);
         break;
diff --git a/src/views/notebook.view.ts b/src/views/notebook.view.ts
index d997962..6fc19ee 100644
--- a/src/views/notebook.view.ts
+++ b/src/views/notebook.view.ts
@@ -232,6 +232,10 @@ export class NotebookView {
             // loads notebook view
             this.refresh();
             break;
+          case 'toggleFavorite':
+            // update favorite collection
+            this.toggleFavorite(message.uri);
+            break;  
           case 'loadView':
             // launch new view
             this.loadView(message.viewName, message.uri);
@@ -384,6 +388,14 @@ export class NotebookView {
     }
   } // end of refreshView()
 
+  /**
+   * Updates favorite collection.
+   * @param notebookUrl Notebook url to add/remove from favorite notebooks collection.
+   */
+  public async toggleFavorite(notebookUrl: string) {
+    notebookManager.addNotebook('favorite', this._notebook);
+  }
+
   /**
    * Saves notebook in requested file formats.
    * @param fileType Notebook file type to save.