diff --git a/src/lib/dom-api-shadow.html b/src/lib/dom-api-shadow.html
index bcd76df482..6a3cc300d7 100644
--- a/src/lib/dom-api-shadow.html
+++ b/src/lib/dom-api-shadow.html
@@ -26,6 +26,28 @@
       return TreeApi.arrayCopy(this.node.querySelectorAll(selector));
     },
 
+    _query: function(matcher, node) {
+      node = node || this.node;
+      var list = [];
+      this._queryElements(node.childNodes, matcher, list);
+      return list;
+    },
+
+    _queryElements: function(elements, matcher, list) {
+      for (var i=0, l=elements.length, c; (i<l) && (c=elements[i]); i++) {
+        if (c.nodeType === Node.ELEMENT_NODE) {
+          this._queryElement(c, matcher, list);
+        }
+      }
+    },
+
+    _queryElement: function(node, matcher, list) {
+      if (matcher(node)) {
+        list.push(node);
+      }
+      this._queryElements(node.childNodes, matcher, list);
+    },
+
     getOwnerRoot: function() {
       var n = this.node;
       while (n) {
@@ -57,7 +79,7 @@
   });
 
   Object.defineProperties(DomApi.prototype, {
-    
+
     childNodes: {
       get: function() {
         return TreeApi.arrayCopyChildNodes(this.node);
@@ -108,7 +130,7 @@
   };
 
   forwardMethods(['cloneNode', 'appendChild', 'insertBefore',
-    'removeChild', 'replaceChild', 'setAttribute', 'removeAttribute', 
+    'removeChild', 'replaceChild', 'setAttribute', 'removeAttribute',
     'querySelector']);
 
   var forwardProperties = function(f$) {
@@ -131,4 +153,4 @@
     'lastElementChild', 'nextElementSibling', 'previousElementSibling']);
 
 })();
-</script>
\ No newline at end of file
+</script>
diff --git a/test/runner.html b/test/runner.html
index 852e54f112..7ae43c2a1c 100644
--- a/test/runner.html
+++ b/test/runner.html
@@ -62,6 +62,7 @@
       // 'unit/styling-cross-scope-apply.html?dom=shadow',
       'unit/styling-cross-scope-unknown-host.html',
       'unit/custom-style.html',
+      'unit/custom-style.html?dom=shadow',
       'unit/custom-style-late.html',
       'unit/dynamic-import.html',
       'unit/templatizer.html',