diff --git a/framework/core/js/src/common/Application.tsx b/framework/core/js/src/common/Application.tsx
index 64e70d18f..5db7fa84e 100644
--- a/framework/core/js/src/common/Application.tsx
+++ b/framework/core/js/src/common/Application.tsx
@@ -433,6 +433,8 @@ export default class Application {
     // a dud response, we don't want the application to crash. We'll show an
     // error message to the user instead.
 
+    // @ts-expect-error Typescript doesn't know we return promisified `ReturnType` OR `string`,
+    // so it errors due to Mithril's typings
     const defaultDeserialize = (response: string) => response as ResponseType;
 
     // When extracting the data from the response, we can check the server