diff --git a/closure.log b/closure.log
index 6a95c684de..54cf42428e 100644
--- a/closure.log
+++ b/closure.log
@@ -562,22 +562,8 @@ polymer.html_script_32.js:297: WARNING - Cannot add property selectedItem to a s
             this.selected = this.selectedItem = item;
                             ^^^^^^^^^^^^^^^^^
 
-polymer.html_script_33.js:47: WARNING - Returned type does not match declared return type.
-Expected : HTMLStyleElement|null
-Found    : undefined
-
-        return;
-        ^^^^^^^
-
-polymer.html_script_33.js:55: WARNING - Returned type does not match declared return type.
-Expected : HTMLStyleElement|null
-Found    : Element
-
-      return this._style;
-      ^^^^^^^^^^^^^^^^^^^
-
 polymer.html_script_34.js:5: WARNING - Property _mutablePropertyChange never defined on Polymer.MutableData of type function(?):?
   let mutablePropertyChange = Polymer.MutableData._mutablePropertyChange;
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-0 error(s), 126 warning(s), 75.3% typed
+0 error(s), 124 warning(s), 75.3% typed
diff --git a/lib/elements/custom-style.html b/lib/elements/custom-style.html
index 8aae908d86..037762c7f7 100644
--- a/lib/elements/custom-style.html
+++ b/lib/elements/custom-style.html
@@ -53,9 +53,9 @@
       if (this._style) {
         return this._style;
       }
-      const style = this.querySelector('style');
+      const style = /** @type {HTMLStyleElement} */(this.querySelector('style'));
       if (!style) {
-        return;
+        return null;
       }
       this._style = style;
       const include = style.getAttribute(attr);