diff --git a/packages/html/src/index.ts b/packages/html/src/index.ts
index c22650057..59d74bfcd 100644
--- a/packages/html/src/index.ts
+++ b/packages/html/src/index.ts
@@ -70,7 +70,7 @@ const defaultTemplate = async ({
 
 const supportedFormats = ['es', 'esm', 'iife', 'umd'];
 
-const defaults = {
+const defaults: Required<RollupHtmlOptions> = {
   attributes: {
     link: null,
     html: { lang: 'en' },
@@ -84,11 +84,8 @@ const defaults = {
 };
 
 export default function html(opts: RollupHtmlOptions = {}): Plugin {
-  const { attributes, fileName, meta, publicPath, template, title } = Object.assign(
-    {},
-    defaults,
-    opts
-  );
+  const { attributes, fileName, meta, publicPath, template, title }: Required<RollupHtmlOptions> =
+    Object.assign({}, defaults, opts);
 
   return {
     name: 'html',
diff --git a/packages/html/types/index.d.ts b/packages/html/types/index.d.ts
index 715e9a03c..0b73a54f6 100644
--- a/packages/html/types/index.d.ts
+++ b/packages/html/types/index.d.ts
@@ -15,7 +15,7 @@ export interface RollupHtmlOptions {
   fileName?: string;
   meta?: Record<string, any>[];
   publicPath?: string;
-  template?: (templateoptions: RollupHtmlTemplateOptions) => string;
+  template?: (templateoptions: RollupHtmlTemplateOptions) => string | Promise<string>;
 }
 
 export function makeHtmlAttributes(attributes: Record<string, string>): string;