diff --git a/user/src/com/google/gwt/resources/rebind/context/AbstractClientBundleGenerator.java b/user/src/com/google/gwt/resources/rebind/context/AbstractClientBundleGenerator.java
index 69b78d6..4fe34d3 100644
--- a/user/src/com/google/gwt/resources/rebind/context/AbstractClientBundleGenerator.java
+++ b/user/src/com/google/gwt/resources/rebind/context/AbstractClientBundleGenerator.java
@@ -50,6 +50,7 @@
 import com.google.gwt.user.rebind.ClassSourceFileComposerFactory;
 import com.google.gwt.user.rebind.SourceWriter;
 
+import java.beans.Beans;
 import java.io.PrintWriter;
 import java.io.Serializable;
 import java.net.URL;
@@ -968,6 +969,11 @@
 
     toReturn.append("_" + getClass().getSimpleName());
 
+    // If design time, generate new class each time to allow reloading.
+    if (Beans.isDesignTime()) {
+      toReturn.append("_designTime" + System.currentTimeMillis());
+    }
+
     return toReturn.toString();
   }