diff --git a/src/Container.ts b/src/Container.ts
index 4701ab3ea..af2b98294 100644
--- a/src/Container.ts
+++ b/src/Container.ts
@@ -220,7 +220,7 @@ export abstract class Container<
    *  return node.getType() === 'Shape'
    * })
    */
-  findOne<ChildNode extends Node = Node>(selector: string | Function) {
+  findOne<ChildNode extends Node = Node>(selector: string | Function): ChildNode | undefined {
     var result = this._generalFind<ChildNode>(selector, true);
     return result.length > 0 ? result[0] : undefined;
   }