diff --git a/src/CustomElements/CustomElements.js b/src/CustomElements/CustomElements.js
index 8ef94e6..03f4008 100644
--- a/src/CustomElements/CustomElements.js
+++ b/src/CustomElements/CustomElements.js
@@ -16,9 +16,12 @@ window.CustomElements = window.CustomElements || {flags:{}};
 // Flags. Convert url arguments to flags
 var flags = {};
 if (!flags.noOpts) {
-  location.search.slice(1).split('&').forEach(function(o) {
-    o = o.split('=');
-    o[0] && (flags[o[0]] = o[1] || true);
+  location.search.slice(1).split('&').forEach(function(option) {
+    var parts = option.split('=');
+    var match;
+    if (parts[0] && (match = parts[0].match(/wc-(.+)/))) {
+      flags[match[1]] = parts[1] || true;
+    }
   });
 }
 
diff --git a/src/HTMLImports/HTMLImports.js b/src/HTMLImports/HTMLImports.js
index 2b76f5d..2577c2a 100644
--- a/src/HTMLImports/HTMLImports.js
+++ b/src/HTMLImports/HTMLImports.js
@@ -16,9 +16,12 @@ window.HTMLImports = window.HTMLImports || {flags:{}};
 // Flags. Convert url arguments to flags
 var flags = {};
 if (!flags.noOpts) {
-  location.search.slice(1).split('&').forEach(function(o) {
-    o = o.split('=');
-    o[0] && (flags[o[0]] = o[1] || true);
+  location.search.slice(1).split('&').forEach(function(option) {
+    var parts = option.split('=');
+    var match;
+    if (parts[0] && (match = parts[0].match(/wc-(.+)/))) {
+      flags[match[1]] = parts[1] || true;
+    }
   });
 }
 
diff --git a/src/WebComponents/build/boot-lite.js b/src/WebComponents/build/boot-lite.js
index 4c3a6f4..c1cbca6 100644
--- a/src/WebComponents/build/boot-lite.js
+++ b/src/WebComponents/build/boot-lite.js
@@ -11,19 +11,22 @@ window.WebComponents = window.WebComponents || {};
 
 // process flags
 (function(scope){
-  
+
   // import
   var flags = scope.flags || {};
-  
+
   var file = 'webcomponents-lite.js';
   var script = document.querySelector('script[src*="' + file + '"]');
 
   // Flags. Convert url arguments to flags
   if (!flags.noOpts) {
     // from url
-    location.search.slice(1).split('&').forEach(function(o) {
-      o = o.split('=');
-      o[0] && (flags[o[0]] = o[1] || true);
+    location.search.slice(1).split('&').forEach(function(option) {
+      var parts = option.split('=');
+      var match;
+      if (parts[0] && (match = parts[0].match(/wc-(.+)/))) {
+        flags[match[1]] = parts[1] || true;
+      }
     });
     // from script
     if (script) {
@@ -48,7 +51,7 @@ window.WebComponents = window.WebComponents || {};
   // Determine default settings.
   // If any of these flags match 'native', then force native ShadowDOM; any
   // other truthy value, or failure to detect native
-  // ShadowDOM, results in polyfill 
+  // ShadowDOM, results in polyfill
   flags.shadow = (flags.shadow || flags.shadowdom || flags.polyfill);
   if (flags.shadow === 'native') {
     flags.shadow = false;
diff --git a/src/WebComponents/build/boot.js b/src/WebComponents/build/boot.js
index 54c662f..c15938a 100644
--- a/src/WebComponents/build/boot.js
+++ b/src/WebComponents/build/boot.js
@@ -21,9 +21,12 @@ window.WebComponents = window.WebComponents || {};
   // Flags. Convert url arguments to flags
   if (!flags.noOpts) {
     // from url
-    location.search.slice(1).split('&').forEach(function(o) {
-      o = o.split('=');
-      o[0] && (flags[o[0]] = o[1] || true);
+    location.search.slice(1).split('&').forEach(function(option) {
+      var parts = option.split('=');
+      var match;
+      if (parts[0] && (match = parts[0].match(/wc-(.+)/))) {
+        flags[match[1]] = parts[1] || true;
+      }
     });
     // from script
     if (script) {
diff --git a/tests/ShadowCSS/tests.js b/tests/ShadowCSS/tests.js
index 121ed1d..be7a483 100644
--- a/tests/ShadowCSS/tests.js
+++ b/tests/ShadowCSS/tests.js
@@ -10,19 +10,19 @@
 
 htmlSuite('ShadowCss', function() {
   htmlTest('html/pseudo-scoping.html');
-  htmlTest('html/pseudo-scoping.html?shadow');
+  htmlTest('html/pseudo-scoping.html?wc-shadow');
   htmlTest('html/pseudo-scoping-strict.html');
-  htmlTest('html/pseudo-scoping-strict.html?shadow');
+  htmlTest('html/pseudo-scoping-strict.html?wc-shadow');
   htmlTest('html/polyfill-directive.html');
   htmlTest('html/polyfill-rule.html');
   htmlTest('html/colon-host.html');
-  htmlTest('html/colon-host.html?shadow');
-  htmlTest('html/combinators.html?shadow');
+  htmlTest('html/colon-host.html?wc-shadow');
+  htmlTest('html/combinators.html?wc-shadow');
   htmlTest('html/combinators-shadow.html');
-  htmlTest('html/combinators-shadow.html?shadow');
+  htmlTest('html/combinators-shadow.html?wc-shadow');
   htmlTest('html/compressed.html');
   htmlTest('html/before-content.html');
-  htmlTest('html/before-content.html?shadow');
+  htmlTest('html/before-content.html?wc-shadow');
   htmlTest('html/before-content.html');
   htmlTest('html/style-import.html');
   htmlTest('html/style-import-base-tag.html');
diff --git a/tests/WebComponents/tests.js b/tests/WebComponents/tests.js
index c074ff5..cbdd85c 100644
--- a/tests/WebComponents/tests.js
+++ b/tests/WebComponents/tests.js
@@ -17,10 +17,10 @@ htmlSuite('loader and build', function() {
 htmlSuite('integration', function() {
   htmlTest('html/web-components.html');
   htmlTest('html/smoke.html');
-  htmlTest('html/smoke.html?shadow');
+  htmlTest('html/smoke.html?wc-shadow');
   htmlTest('html/ce-import.html');
   htmlTest('html/ce-upgradedocumenttree.html');
-  htmlTest('html/ce-import.html?shadow');
+  htmlTest('html/ce-import.html?wc-shadow');
   htmlTest('html/ce-upgrade-order.html');
 });
 
diff --git a/webcomponents-lite.js b/webcomponents-lite.js
index b7a8d29..270a842 100644
--- a/webcomponents-lite.js
+++ b/webcomponents-lite.js
@@ -21,9 +21,12 @@
   var flags = {};
   if (!flags.noOpts) {
     // from url
-    location.search.slice(1).split('&').forEach(function(o) {
-      o = o.split('=');
-      o[0] && (flags[o[0]] = o[1] || true);
+    location.search.slice(1).split('&').forEach(function(option) {
+      var parts = option.split('=');
+      var match;
+      if (parts[0] && (match = parts[0].match(/wc-(.+)/))) {
+        flags[match[1]] = parts[1] || true;
+      }
     });
     // from script
     if (script) {
diff --git a/webcomponents.js b/webcomponents.js
index 8112c73..9fd4b7f 100644
--- a/webcomponents.js
+++ b/webcomponents.js
@@ -21,9 +21,12 @@
   var flags = {};
   if (!flags.noOpts) {
     // from url
-    location.search.slice(1).split('&').forEach(function(o) {
-      o = o.split('=');
-      o[0] && (flags[o[0]] = o[1] || true);
+    location.search.slice(1).split('&').forEach(function(option) {
+      var parts = option.split('=');
+      var match;
+      if (parts[0] && (match = parts[0].match(/wc-(.+)/))) {
+        flags[match[1]] = parts[1] || true;
+      }
     });
     // from script
     if (script) {