diff --git a/closure.log b/closure.log
index 58621a3970..bbd7cf4588 100644
--- a/closure.log
+++ b/closure.log
@@ -514,11 +514,7 @@ Found    : PropertyEffects
           klass.observers : [];
           ^^^^^^^^^^^^^^^
 
-/polymer.html_script_11.js:155: WARNING - Type annotation references non-existent type Objecg.
-     * @return {Objecg} The input `flattenedProps` bag
-                ^^^^^^
-
-/polymer.html_script_11.js:184: WARNING - Property prototype never defined on klass of type HTMLElement{__classProperties:?}
+/polymer.html_script_11.js:184: WARNING - Property prototype never defined on klass of type HTMLElement{__classProperties:Object|null}
         let superCtor = Object.getPrototypeOf(klass.prototype).constructor;
                                               ^^^^^^^^^^^^^^^
 
@@ -761,14 +757,6 @@ Found    : PolymerElement
             return this.splice(arrayOrPath, index, 1);
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-/polymer.html_script_23.js:49: WARNING - Invalid type for parameter 1 of function _mixinBehaviors.
-Expected : {length:?} (loose)
-Found    : Array<?>|null
-More details:
-The found type is a union that includes an unexpected type: null
-      klass = _mixinBehaviors(behaviors, klass);
-                              ^^^^^^^^^
-
 /polymer.html_script_23.js:141: WARNING - Property is never defined on this of type PolymerGenerated
             Polymer.DomModule.import(this.is, 'template') ||
                                      ^^^^^^^
@@ -1495,4 +1483,4 @@ externs/closure-types.js:759: WARNING - property toggle on interface Polymer_Arr
 Polymer_ArraySelectorMixin.prototype.toggle;
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-0 error(s), 328 warning(s), 72.6% typed
+0 error(s), 326 warning(s), 72.6% typed
diff --git a/lib/legacy/class.html b/lib/legacy/class.html
index a63c6a16a7..626750ac61 100644
--- a/lib/legacy/class.html
+++ b/lib/legacy/class.html
@@ -35,7 +35,7 @@
      * to ensure that any legacy behaviors can rely on legacy Polymer API on
      * the underlying element.
      *
-     * @param {Object|Array} behaviors Behavior object or array of behaviors.
+     * @param {!(Object|Array)} behaviors Behavior object or array of behaviors.
      * @param {HTMLElement} klass Element class.
      * @return {HTMLElement} Returns a new Element class extended by the
      * passed in `behaviors` and also by `Polymer.LegacyElementMixin`.
@@ -110,7 +110,7 @@
      * @param {Array} behaviors List of behaviors to flatten.
      * @param {Array=} list Target list to flatten behaviors into.
      * @param {Array=} exclude List of behaviors to exclude from the list.
-     * @return {Array} Returns the list of flattened behaviors.
+     * @return {!Array} Returns the list of flattened behaviors.
      */
     function flattenBehaviors(behaviors, list, exclude) {
       list = list || [];
diff --git a/lib/legacy/legacy-element-mixin.html b/lib/legacy/legacy-element-mixin.html
index fa1e699267..c809d3ff32 100644
--- a/lib/legacy/legacy-element-mixin.html
+++ b/lib/legacy/legacy-element-mixin.html
@@ -42,9 +42,9 @@
 
     /**
      * @constructor
-     * @extends {base}
-     * @implements {Polymer_GestureEventListeners}
      * @implements {Polymer_ElementMixin}
+     * @implements {Polymer_GestureEventListeners}
+     * @extends {base}
      */
     const legacyElementBase = Polymer.GestureEventListeners(Polymer.ElementMixin(base));
 
diff --git a/lib/mixins/element-mixin.html b/lib/mixins/element-mixin.html
index 4bef530fb2..4e9fa3c7bc 100644
--- a/lib/mixins/element-mixin.html
+++ b/lib/mixins/element-mixin.html
@@ -170,7 +170,7 @@
      *
      * @param {Object} flattenedProps Bag to collect flattened properties into
      * @param {Object} props Bag of properties to add to `flattenedProps`
-     * @return {Objecg} The input `flattenedProps` bag
+     * @return {Object} The input `flattenedProps` bag
      * @private
      */
     function flattenProperties(flattenedProps, props) {