diff -r 51c86f17f7eb js/src/jsproxy.cpp
--- a/js/src/jsproxy.cpp	Mon Aug 20 17:00:28 2012 +0200
+++ b/js/src/jsproxy.cpp	Mon Aug 20 17:01:48 2012 +0200
@@ -1727,21 +1727,59 @@ ScriptedDirectProxyHandler::delete_(JSCo
     }
 
     // step 8
     // FIXME: API does not include a Throw parameter 
     *bp = false;
     return true;
 }
 
+// 12.6.4 The for-in Statement, step 6
 bool
-ScriptedDirectProxyHandler::enumerate(JSContext *cx, JSObject *proxy, AutoIdVector &props)
+ScriptedDirectProxyHandler::enumerate(JSContext *cx, JSObject *proxy_, AutoIdVector &props)
 {
-    JS_NOT_REACHED("not yet implemented");
-    return false;
+    RootedObject proxy(cx, proxy_);
+
+    // step a
+    RootedObject handler(cx, GetDirectProxyHandlerObject(proxy));
+
+    // step b
+    RootedObject target(cx, GetProxyTargetObject(proxy));
+
+    // step c
+    RootedValue trap(cx);
+    if (!handler->getProperty(cx, ATOM(enumerate), &trap))
+        return false;
+
+    // step d
+    if (trap.isUndefined())
+        return DirectProxyHandler::enumerate(cx, proxy_, props);
+
+    // step e
+    Value argv[] = {
+        ObjectOrNullValue(target)
+    };
+    RootedValue trapResult(cx);
+    if (!Invoke(cx, ObjectValue(*handler), trap, 1, argv, trapResult.address()))
+        return false;
+
+    // step f 
+    if (trapResult.isPrimitive()) {
+        JSAutoByteString bytes;
+        if (!js_AtomToPrintableString(cx, ATOM(enumerate), &bytes)) 
+            return false;
+        RootedValue v(cx, ObjectOrNullValue(proxy));
+        js_ReportValueError2(cx, JSMSG_INVALID_TRAP_RESULT, JSDVG_SEARCH_STACK,
+                             v, NullPtr(), bytes.ptr());
+        return false;
+    }
+
+    // steps g-m are shared 
+    // FIXME: the trap should return an iterator object, see bug 783826
+    return ArrayToIdVector(cx, proxy, target, trapResult, props, ATOM(enumerate));
 }
 
 bool
 ScriptedDirectProxyHandler::has(JSContext *cx, JSObject *proxy, jsid id, bool *bp)
 {
     JS_NOT_REACHED("not yet implemented");
     return false;
 }