diff --git a/ext/js/pages/settings/dictionary-controller.js b/ext/js/pages/settings/dictionary-controller.js
index 0132fe9e18..81b781dae2 100644
--- a/ext/js/pages/settings/dictionary-controller.js
+++ b/ext/js/pages/settings/dictionary-controller.js
@@ -716,9 +716,9 @@ export class DictionaryController {
     /** */
     _onDictionaryMoveButtonClick() {
         const modal = /** @type {import('./modal.js').Modal} */ (this._modalController.getModal('dictionary-move-location'));
-        const {index} = modal.node.dataset;
-        if (typeof index !== 'number') { return; }
+        const index = modal.node.dataset.index ?? '';
         const indexNumber = Number.parseInt(index, 10);
+        if (Number.isNaN(indexNumber)) { return; }
 
         /** @type {HTMLInputElement} */
         const targetStringInput = querySelectorNotNull(document, '#dictionary-move-location');