diff --git a/mozilla/js/rhino/src/org/mozilla/javascript/ScriptableObject.java b/mozilla/js/rhino/src/org/mozilla/javascript/ScriptableObject.java
index 838e9d0bb44..46ad423e2ec 100644
--- a/mozilla/js/rhino/src/org/mozilla/javascript/ScriptableObject.java
+++ b/mozilla/js/rhino/src/org/mozilla/javascript/ScriptableObject.java
@@ -1581,6 +1581,9 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
       if (setter != NOT_FOUND && !(setter instanceof Callable)) {
         throw ScriptRuntime.notFunctionError(setter);
       }
+      if (isDataDescriptor(desc) && isAccessorDescriptor(desc)) {
+         throw ScriptRuntime.typeError0("msg.both.data.and.accessor.desc");
+      }
 
       if (slot == null) { // new property
         if (!isExtensible()) throw ScriptRuntime.typeError("msg.not.extensible");
diff --git a/mozilla/js/rhino/src/org/mozilla/javascript/resources/Messages.properties b/mozilla/js/rhino/src/org/mozilla/javascript/resources/Messages.properties
index 874b6094fdf..4c9b1391fd4 100644
--- a/mozilla/js/rhino/src/org/mozilla/javascript/resources/Messages.properties
+++ b/mozilla/js/rhino/src/org/mozilla/javascript/resources/Messages.properties
@@ -680,6 +680,9 @@ msg.modify.sealed =\
 msg.modify.readonly =\
     Cannot modify readonly property: {0}.
 
+msg.both.data.and.accessor.desc =\
+    Cannot be both a data and an accessor descriptor.
+
 msg.change.configurable.false.to.true =\
     Cannot change the configurable attribute of "{0}" from false to true.