diff --git a/setup_dev_packages b/setup_dev_packages
index 64d063e..4ea2069 100755
--- a/setup_dev_packages
+++ b/setup_dev_packages
@@ -1,12 +1,15 @@
 #!/bin/bash
 
-# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+# Emerges necessary packages for building and testing the update engine. This
+# allows incremental building, bypassing ebuild dependency resolution.
+
 set -ex
 
-sudo USE="-crash cros-debug" emerge -DNauv1 \
+sudo USE="-crash cros-debug" emerge -DNuv1 --selective=n "$@" \
   chromeos-base/hard-host-depends \
   chromeos-base/libchrome \
   chromeos-base/metrics \
@@ -15,5 +18,4 @@
   dev-cpp/gtest \
   dev-util/bsdiff \
   dev-util/lcov \
-  sys-apps/fakeroot \
   sys-apps/rootdev