diff --git a/src/asset_manager/view/FileUploader.ts b/src/asset_manager/view/FileUploader.ts
index 9ef69c8e5..ec51c40ee 100644
--- a/src/asset_manager/view/FileUploader.ts
+++ b/src/asset_manager/view/FileUploader.ts
@@ -392,7 +392,7 @@ export default class FileUploaderView extends View {
       promises.push(promise);
     }
 
-    Promise.all(promises).then(
+    return Promise.all(promises).then(
       data => {
         response.data = data;
         // @ts-ignore
diff --git a/src/utils/fetch.ts b/src/utils/fetch.ts
index 9205fe6c5..32c4285cb 100644
--- a/src/utils/fetch.ts
+++ b/src/utils/fetch.ts
@@ -1,4 +1,3 @@
-// @ts-ignore
 import Promise from 'promise-polyfill';
 import { hasWin } from './mixins';
 
@@ -10,7 +9,7 @@ export default typeof fetch == 'function'
   ? // @ts-ignore
     fetch.bind()
   : (url: string, options: Record<string, any>) => {
-      return new Promise((res: any, rej: any) => {
+      return new Promise((res, rej) => {
         const req = new XMLHttpRequest();
         req.open(options.method || 'get', url);
         req.withCredentials = options.credentials == 'include';
diff --git a/src/utils/promise-polyfill.d.ts b/src/utils/promise-polyfill.d.ts
new file mode 100644
index 000000000..7a63bf53c
--- /dev/null
+++ b/src/utils/promise-polyfill.d.ts
@@ -0,0 +1,4 @@
+declare module 'promise-polyfill' {
+  const defType: PromiseConstructor;
+  export default defType;
+}