diff --git a/lib/mixins/gesture-event-listeners.js b/lib/mixins/gesture-event-listeners.js
index 355a9285d2..37dc78bb97 100644
--- a/lib/mixins/gesture-event-listeners.js
+++ b/lib/mixins/gesture-event-listeners.js
@@ -30,7 +30,11 @@ const gestures = gestures$0;
  * gesture events to nodes
  */
 export const GestureEventListeners = dedupingMixin(
-    /** @param {function(new:HTMLElement)} superClass */
+    /**
+     * @template T
+     * @param {function(new:T)} superClass Class to apply mixin to.
+     * @return {function(new:T)} superClass with mixin applied.
+     */
     (superClass) => {
       /**
        * @polymer
diff --git a/lib/mixins/properties-changed.js b/lib/mixins/properties-changed.js
index 56089d5d4d..118f010c6e 100644
--- a/lib/mixins/properties-changed.js
+++ b/lib/mixins/properties-changed.js
@@ -34,7 +34,11 @@ const microtask = microTask;
  *   generated property accessors.
  */
 export const PropertiesChanged = dedupingMixin(
-    /** @param {function(new:HTMLElement)} superClass */
+    /**
+     * @template T
+     * @param {function(new:T)} superClass Class to apply mixin to.
+     * @return {function(new:T)} superClass with mixin applied.
+     */
     (superClass) => {
 
   /**
@@ -175,13 +179,14 @@ export const PropertiesChanged = dedupingMixin(
      * bindings.  `super.ready()` must be called to ensure the data system
      * becomes enabled.
      *
-     * @return {void|!Promise<void>}
+     * @return {void|!Promise<void>} void
      * @public
      * @override
      */
     ready() {
       this.__dataReady = true;
       this._flushProperties();
+      return undefined;
     }
 
     /**
diff --git a/lib/mixins/template-stamp.js b/lib/mixins/template-stamp.js
index f96909f54c..14b5e1a9ad 100644
--- a/lib/mixins/template-stamp.js
+++ b/lib/mixins/template-stamp.js
@@ -106,7 +106,11 @@ function createNodeEventHandler(context, eventName, methodName) {
  * @summary Element class mixin that provides basic template parsing and stamping
  */
 export const TemplateStamp = dedupingMixin(
-    /** @param {function(new:HTMLElement)} superClass */
+    /**
+     * @template T
+     * @param {function(new:T)} superClass Class to apply mixin to.
+     * @return {function(new:T)} superClass with mixin applied.
+     */
     (superClass) => {
 
   /**