diff --git a/types/lib/legacy/class.d.ts b/types/lib/legacy/class.d.ts
index fe4124a07f..52d2ff8677 100644
--- a/types/lib/legacy/class.d.ts
+++ b/types/lib/legacy/class.d.ts
@@ -91,5 +91,5 @@ declare namespace Polymer {
    *
    * @returns Generated class
    */
-  function Class(info: PolymerInit): {new(): HTMLElement};
+  function Class(info: PolymerInit, mixin: (p0: T|null) => T|null): {new(): HTMLElement};
 }
diff --git a/types/lib/legacy/legacy-element-mixin.d.ts b/types/lib/legacy/legacy-element-mixin.d.ts
index 6f4d187381..40c4be507f 100644
--- a/types/lib/legacy/legacy-element-mixin.d.ts
+++ b/types/lib/legacy/legacy-element-mixin.d.ts
@@ -30,6 +30,7 @@ declare namespace Polymer {
 
   interface LegacyElementMixinConstructor {
     new(...args: any[]): LegacyElementMixin;
+    _finalizeClass(): void;
   }
 
   interface LegacyElementMixin extends Polymer.ElementMixin, Polymer.PropertyEffects, Polymer.TemplateStamp, Polymer.PropertyAccessors, Polymer.PropertiesChanged, Polymer.PropertiesMixin, Polymer.GestureEventListeners {
diff --git a/types/lib/mixins/element-mixin.d.ts b/types/lib/mixins/element-mixin.d.ts
index 907b0493a1..c0d43eb01d 100644
--- a/types/lib/mixins/element-mixin.d.ts
+++ b/types/lib/mixins/element-mixin.d.ts
@@ -223,11 +223,4 @@ declare namespace Polymer {
      */
     resolveUrl(url: string, base?: string): string;
   }
-
-  /**
-   * Provides basic tracking of element definitions (registrations) and
-   * instance counts.
-   */
-  namespace telemetry {
-  }
 }
diff --git a/types/lib/utils/boot.d.ts b/types/lib/utils/boot.d.ts
index 4175f31846..3b07397343 100644
--- a/types/lib/utils/boot.d.ts
+++ b/types/lib/utils/boot.d.ts
@@ -16,4 +16,11 @@
  *   own custom HTML elements.
  */
 declare namespace Polymer {
+
+  /**
+   * Provides basic tracking of element definitions (registrations) and
+   * instance counts.
+   */
+  namespace telemetry {
+  }
 }
diff --git a/types/lib/utils/settings.d.ts b/types/lib/utils/settings.d.ts
index b2f90ffe76..17364c51c1 100644
--- a/types/lib/utils/settings.d.ts
+++ b/types/lib/utils/settings.d.ts
@@ -37,4 +37,11 @@ declare namespace Polymer {
    * Sets `passiveTouchGestures` globally for all elements using Polymer Gestures.
    */
   function setPassiveTouchGestures(usePassive: boolean): void;
+
+
+  /**
+   * Sets `legacyOptimizations` globally for all elements. Enables
+   * optimizations when only legacy Polymer() style elements are used.
+   */
+  function setLegacyOptimizations(useLegacyOptimizations: boolean): void;
 }