diff --git a/lib/legacy/class.d.ts b/lib/legacy/class.d.ts
index b39544877..44c47ce95 100644
--- a/lib/legacy/class.d.ts
+++ b/lib/legacy/class.d.ts
@@ -86,6 +86,6 @@ export {Class};
  *
  * @returns Generated class
  */
-declare function Class<T>(info: PolymerInit, mixin: (p0: T) => T): {new(): HTMLElement};
+declare function Class<T>(info: PolymerInit, mixin?: (p0: T) => T): {new(): HTMLElement};
 
 import {PolymerInit} from '../../interfaces';
diff --git a/lib/legacy/polymer-fn.d.ts b/lib/legacy/polymer-fn.d.ts
index 57a26a66e..9180170f8 100644
--- a/lib/legacy/polymer-fn.d.ts
+++ b/lib/legacy/polymer-fn.d.ts
@@ -16,8 +16,9 @@ import {Class} from './class.js';
  *
  * @returns Generated class
  */
-declare function Polymer(info: PolymerInit): {new(): HTMLElement};
-
-export {Polymer};
+export const Polymer: {
+  (info: PolymerInit): {new(): HTMLElement};
+  Class: typeof Class;
+}
 
 import {PolymerInit} from '../../interfaces';
diff --git a/lib/utils/settings.d.ts b/lib/utils/settings.d.ts
index 9972531fa..ab281c282 100644
--- a/lib/utils/settings.d.ts
+++ b/lib/utils/settings.d.ts
@@ -153,3 +153,5 @@ export {setUseAdoptedStyleSheetsWithBuiltCSS};
  * Sets `useAdoptedStyleSheetsWithBuiltCSS` globally.
  */
 declare function setUseAdoptedStyleSheetsWithBuiltCSS(value: boolean): void;
+
+export let legacyOptimizations: boolean;