diff --git a/packages/plugin-outline-pane/src/main.ts b/packages/plugin-outline-pane/src/main.ts
index 383b3f7ad..c9062ea68 100644
--- a/packages/plugin-outline-pane/src/main.ts
+++ b/packages/plugin-outline-pane/src/main.ts
@@ -140,7 +140,7 @@ export class OutlineMain implements ISensor, ITreeBoard, IScrollable {
     const { nodes } = dragObject;
 
     const tree = this._master?.currentTree;
-    if (!tree || !this._shell) {
+    if (!tree || !tree.root || !this._shell) {
       return null;
     }
 
diff --git a/packages/plugin-outline-pane/src/tree.ts b/packages/plugin-outline-pane/src/tree.ts
index ceaebda38..894360cb7 100644
--- a/packages/plugin-outline-pane/src/tree.ts
+++ b/packages/plugin-outline-pane/src/tree.ts
@@ -7,8 +7,11 @@ export class Tree {
 
   readonly id: string;
 
-  @computed get root(): TreeNode {
-    return this.getTreeNode(this.document.focusNode!);
+  @computed get root(): TreeNode | null {
+    if (this.document.focusNode) {
+      return this.getTreeNode(this.document.focusNode!);
+    }
+    return null;
   }
 
   constructor(readonly document: DocumentModel) {
diff --git a/packages/plugin-outline-pane/src/views/tree.tsx b/packages/plugin-outline-pane/src/views/tree.tsx
index f1b2c5c9b..cfe07e0e3 100644
--- a/packages/plugin-outline-pane/src/views/tree.tsx
+++ b/packages/plugin-outline-pane/src/views/tree.tsx
@@ -150,6 +150,9 @@ export default class TreeView extends Component<{ tree: Tree }> {
   render() {
     const { tree } = this.props;
     const { root } = tree;
+    if (!root) {
+      return null;
+    }
     return (
       <div
         className="lc-outline-tree"