diff --git a/core-xhr.html b/core-xhr.html
index dbc531b..0a7ef4d 100644
--- a/core-xhr.html
+++ b/core-xhr.html
@@ -77,7 +77,13 @@
         for (var n in params) {
           var v = params[n];
           n = encodeURIComponent(n);
-          r.push(v == null ? n : (n + '=' + encodeURIComponent(v)));
+          if (Array.isArray(v)) {
+            v.forEach(function(val) {
+              r.push(val == null ? n : (n + '=' + encodeURIComponent(val)));
+            });
+          } else {
+            r.push(v == null ? n : (n + '=' + encodeURIComponent(v)));
+          }
         }
         return r.join('&');
       },
diff --git a/tests/html/core-ajax.html b/tests/html/core-ajax.html
index 318d052..0c4fd27 100644
--- a/tests/html/core-ajax.html
+++ b/tests/html/core-ajax.html
@@ -11,7 +11,7 @@
 <head>
   <title>core-ajax</title>
 
-  <script src="../../../webcomponentsjs/webcomponents.js"></script>
+  <script src="../../../webcomponents.js/webcomponents.js"></script>
   <script src="../../../polymer-test-tools/chai/chai.js"></script>
   <script src="../../../polymer-test-tools/htmltest.js"></script>
 
@@ -21,20 +21,35 @@
 <body>
 
   <core-ajax
+    id="simple"
     url="http://gdata.youtube.com/feeds/api/videos/"
     params='{"alt":"json", "q":"chrome"}'
     handleAs="json"
     auto></core-ajax>
 
+  <core-ajax
+    id="array-params"
+    url="http://gdata.youtube.com/feeds/api/videos/"
+    params='{"alt":"json", "q":"chrome", "keywords":["chrome", "browser"]}'
+    handleAs="json"
+    auto></core-ajax>
+
   <script>
 
     document.addEventListener('polymer-ready', function() {
       var assert = chai.assert;
-      var ajax = document.querySelector('core-ajax');
+      var ajax = document.querySelector('#simple');
       ajax.addEventListener("core-response", function(event) {
         assert.isTrue(event.detail.response.feed.entry.length > 0);
         done();
       });
+
+      var arrayParamAjax = document.querySelector('#array-params');
+      arrayParamAjax.addEventListener("core-complete", function(event) {
+        assert.isTrue(/[?&]keywords=browser/.test(event.detail.xhr.responseURL));
+        assert.isTrue(/[?&]keywords=chrome/.test(event.detail.xhr.responseURL));
+        done();
+      });
     });
 
   </script>
