diff --git a/circuit-construction-kit-dc_en.html b/circuit-construction-kit-dc_en.html
index eb10634..2c85a21 100644
--- a/circuit-construction-kit-dc_en.html
+++ b/circuit-construction-kit-dc_en.html
@@ -27,6 +27,7 @@
 
   // Preloads, with more included for phet-io brand
   let preloads = [
+    '../phet-core/js/phet-polyfill.js',
     '../joist/js/splash.js',
     '../sherpa/lib/jquery-2.1.0.js',
     '../sherpa/lib/lodash-4.17.4.js',