diff --git a/mopidy/__main__.py b/mopidy/__main__.py
index f571e0ff..f66ac6c1 100644
--- a/mopidy/__main__.py
+++ b/mopidy/__main__.py
@@ -40,11 +40,13 @@ def main():
     signal.signal(signal.SIGUSR1, pykka.debug.log_thread_tracebacks)
 
     try:
+        registry = ext.Registry()
+
         root_cmd = commands.RootCommand()
         config_cmd = commands.ConfigCommand()
         deps_cmd = commands.DepsCommand()
 
-        root_cmd.set(extension=None)
+        root_cmd.set(extension=None, registry=registry)
         root_cmd.add_child('config', config_cmd)
         root_cmd.add_child('deps', deps_cmd)
 
@@ -108,7 +110,7 @@ def main():
             return 1
 
         for extension in enabled_extensions:
-            extension.setup()
+            extension.setup(registry)
 
         # Anything that wants to exit after this point must use
         # mopidy.utils.process.exit_process as actors can have been started.
diff --git a/mopidy/backends/local/commands.py b/mopidy/backends/local/commands.py
index 8a951929..2f6f744e 100644
--- a/mopidy/backends/local/commands.py
+++ b/mopidy/backends/local/commands.py
@@ -4,7 +4,7 @@ import logging
 import os
 import time
 
-from mopidy import commands, exceptions, ext
+from mopidy import commands, exceptions
 from mopidy.audio import scan
 from mopidy.utils import path
 
@@ -30,7 +30,7 @@ class ScanCommand(commands.Command):
             file_ext.lower() for file_ext in excluded_file_extensions)
 
         # TODO: select updater / library to use by name
-        updaters = ext.registry['local:library']
+        updaters = args.registry['local:library']
         if not updaters:
             logger.error('No usable library updaters found.')
             return 1
diff --git a/mopidy/commands.py b/mopidy/commands.py
index 372550a0..1bba63fa 100644
--- a/mopidy/commands.py
+++ b/mopidy/commands.py
@@ -9,7 +9,7 @@ import sys
 import glib
 import gobject
 
-from mopidy import config as config_lib, ext
+from mopidy import config as config_lib
 from mopidy.audio import Audio
 from mopidy.core import Core
 from mopidy.utils import deps, process, versioning
@@ -260,8 +260,8 @@ class RootCommand(Command):
     def run(self, args, config):
         loop = gobject.MainLoop()
 
-        backend_classes = ext.registry['backend']
-        frontend_classes = ext.registry['frontend']
+        backend_classes = args.registry['backend']
+        frontend_classes = args.registry['frontend']
 
         try:
             audio = self.start_audio(config)
diff --git a/mopidy/ext.py b/mopidy/ext.py
index d1c81dc5..c79ebe40 100644
--- a/mopidy/ext.py
+++ b/mopidy/ext.py
@@ -62,7 +62,7 @@ class Extension(object):
         """
         pass
 
-    def setup(self):
+    def setup(self, registry):
         for backend_class in self.get_backend_classes():
             registry.add('backend', backend_class)
 
@@ -125,15 +125,16 @@ class Extension(object):
         pass
 
 
-class _Registry(collections.Mapping):
+# TODO: document
+class Registry(collections.Mapping):
     def __init__(self):
-        self._registry = collections.defaultdict(list)
+        self._registry = {}
 
     def add(self, name, cls):
-        self._registry[name].append(cls)
+        self._registry.setdefault(name, []).append(cls)
 
     def __getitem__(self, name):
-        return self._registry[name]
+        return self._registry.setdefault(name, [])
 
     def __iter__(self):
         return iter(self._registry)
@@ -142,12 +143,6 @@ class _Registry(collections.Mapping):
         return len(self._registry)
 
 
-# TODO: document the registry
-# TODO: consider if we should avoid having this as a global and pass an
-#       instance from __main__ around instead?
-registry = _Registry()
-
-
 def load_extensions():
     """Find all installed extensions.