diff --git a/src/ApiFormMixin.d.ts b/src/ApiFormMixin.d.ts
index 1c7aae7..7baf8d3 100644
--- a/src/ApiFormMixin.d.ts
+++ b/src/ApiFormMixin.d.ts
@@ -3,6 +3,14 @@ import {IronFormElement} from '@polymer/iron-form';
 
 export {ApiFormMixin};
 
+declare function ApiFormMixin<T extends new (...args: any[]) => {}>(base: T): T & ApiFormMixinConstructor;
+
+interface ApiFormMixinConstructor {
+  new(...args: any[]): ApiFormMixin;
+}
+
+export {ApiFormMixinConstructor};
+
 /**
  * A mixin to be implemented to elements that processes AMF data via form
  * data model and displays forms from the model.
@@ -176,5 +184,3 @@ interface ApiFormMixin {
    */
   _gaEvent(category: string, action: string, label?: string): void;
 }
-
-declare const ApiFormMixin: object;
diff --git a/test/test-element.js b/test/test-element.js
index 12bfd7e..8d672c8 100644
--- a/test/test-element.js
+++ b/test/test-element.js
@@ -3,9 +3,8 @@ import { ApiFormMixin } from '../api-form-mixin.js';
 import '@polymer/iron-form/iron-form.js';
 import styles from '../api-form-styles.js';
 /**
- * @customElement
- * @demo demo/index.html
- * @appliesMixin ApiFormMixin
+ * @mixes ApiFormMixin
+ * @extends LitElement
  */
 class TestElement extends ApiFormMixin(LitElement) {
   static get styles() {