Make the field volatile.
diff --git a/org.eclipse.gemini.web.core/src/main/java/org/eclipse/gemini/web/internal/url/WebBundleUrl.java b/org.eclipse.gemini.web.core/src/main/java/org/eclipse/gemini/web/internal/url/WebBundleUrl.java
index 380e097..ff2a6c8 100644
--- a/org.eclipse.gemini.web.core/src/main/java/org/eclipse/gemini/web/internal/url/WebBundleUrl.java
+++ b/org.eclipse.gemini.web.core/src/main/java/org/eclipse/gemini/web/internal/url/WebBundleUrl.java
@@ -50,7 +50,7 @@
 
     private final String location;
 
-    private Map<String, String> options;
+    private volatile Map<String, String> options;
 
     public WebBundleUrl(String location, Map<String, String> options) throws MalformedURLException {
         this.url = createURL(location, options);