diff --git a/scripts/celerity_mapper.php b/scripts/celerity_mapper.php
index d281da41ce..7fa40e2d87 100755
--- a/scripts/celerity_mapper.php
+++ b/scripts/celerity_mapper.php
@@ -111,12 +111,24 @@ foreach ($file_map as $path => $info) {
 $package_map = array();
 foreach ($package_spec as $name => $package) {
   $hashes = array();
+  $type = null;
   foreach ($package as $symbol) {
     if (empty($hash_map[$symbol])) {
       throw new Exception(
         "Package specification for '{$name}' includes '{$symbol}', but that ".
         "symbol is not defined anywhere.");
     }
+    if ($type === null) {
+      $type = $runtime_map[$symbol]['type'];
+    } else {
+      $ntype = $runtime_map[$symbol]['type'];
+      if ($type !== $ntype) {
+        throw new Exception(
+          "Package specification for '{$name}' mixes resources of type ".
+          "'{$type}' with resources of type '{$ntype}'. Each package may only ".
+          "contain one type of resource.");
+      }
+    }
     $hashes[] = $symbol.':'.$hash_map[$symbol];
   }
   $key = substr(md5(implode("\n", $hashes)), 0, 8);
@@ -124,7 +136,7 @@ foreach ($package_spec as $name => $package) {
     'name'    => $name,
     'symbols' => $package,
     'uri'     => '/res/pkg/'.$key.'/'.$name,
-    'type'    => 'css', // TODO LOL
+    'type'    => $type,
   );
   foreach ($package as $symbol) {
     $package_map['reverse'][$symbol] = $key;
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 94cf87f8f7..74defb7455 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -97,6 +97,7 @@ phutil_register_library_map(array(
     'DifferentialUnitStatus' => 'applications/differential/constants/unitstatus',
     'Javelin' => 'infratructure/javelin/api',
     'LiskDAO' => 'storage/lisk/dao',
+    'Phabricator404Controller' => 'applications/base/controller/404',
     'PhabricatorAuthController' => 'applications/auth/controlller/base',
     'PhabricatorConduitAPIController' => 'applications/conduit/controller/api',
     'PhabricatorConduitConnectionLog' => 'applications/conduit/storage/connectionlog',
@@ -240,6 +241,7 @@ phutil_register_library_map(array(
     'DifferentialRevisionListController' => 'DifferentialController',
     'DifferentialRevisionUpdateHistoryView' => 'AphrontView',
     'DifferentialRevisionViewController' => 'DifferentialController',
+    'Phabricator404Controller' => 'PhabricatorController',
     'PhabricatorAuthController' => 'PhabricatorController',
     'PhabricatorConduitAPIController' => 'PhabricatorConduitController',
     'PhabricatorConduitConnectionLog' => 'PhabricatorConduitDAO',
diff --git a/src/aphront/applicationconfiguration/AphrontApplicationConfiguration.php b/src/aphront/applicationconfiguration/AphrontApplicationConfiguration.php
index 32f9bbef9b..cba9578bb4 100644
--- a/src/aphront/applicationconfiguration/AphrontApplicationConfiguration.php
+++ b/src/aphront/applicationconfiguration/AphrontApplicationConfiguration.php
@@ -28,6 +28,7 @@ abstract class AphrontApplicationConfiguration {
   abstract public function getApplicationName();
   abstract public function getURIMap();
   abstract public function buildRequest();
+  abstract public function build404Controller();
 
   final public function setRequest(AphrontRequest $request) {
     $this->request = $request;
@@ -45,6 +46,10 @@ abstract class AphrontApplicationConfiguration {
     $path = $request->getPath();
     list($controller_class, $uri_data) = $mapper->mapPath($path);
 
+    if (!$controller_class) {
+      return $this->build404Controller();
+    }
+
     PhutilSymbolLoader::loadClass($controller_class);
     $controller = newv($controller_class, array($request));
 
diff --git a/src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php b/src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php
index a5553423ee..c81c7a6c7a 100644
--- a/src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php
+++ b/src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php
@@ -155,5 +155,9 @@ class AphrontDefaultApplicationConfiguration
     return $response;
   }
 
+  public function build404Controller() {
+    return new Phabricator404Controller($request);
+  }
+
 
 }
diff --git a/src/applications/base/controller/404/Phabricator404Controller.php b/src/applications/base/controller/404/Phabricator404Controller.php
new file mode 100644
index 0000000000..591e7a3c3e
--- /dev/null
+++ b/src/applications/base/controller/404/Phabricator404Controller.php
@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class Phabricator404Controller extends PhabricatorController {
+
+  public function processRequest() {
+    return new Aphront404Response();
+  }
+
+}