diff --git a/src/panels/lovelace/hui-root.ts b/src/panels/lovelace/hui-root.ts
index a73150685a..162d59acca 100644
--- a/src/panels/lovelace/hui-root.ts
+++ b/src/panels/lovelace/hui-root.ts
@@ -417,7 +417,7 @@ class HUIRoot extends hassLocalizeLitMixin(LitElement) {
     return this.shadowRoot!.getElementById("view") as HTMLDivElement;
   }
 
-  private _routeDataChanged(ev) {
+  private _routeDataChanged(ev): void {
     this.routeData = ev.detail.value;
   }