diff --git a/mopidy/backends/stream/__init__.py b/mopidy/backends/stream/__init__.py
index 47dd6151..e4c2bad7 100644
--- a/mopidy/backends/stream/__init__.py
+++ b/mopidy/backends/stream/__init__.py
@@ -26,6 +26,6 @@ class Extension(ext.Extension):
     def validate_environment(self):
         pass
 
-    def get_backend_classes(self):
+    def setup(self, registry):
         from .actor import StreamBackend
-        return [StreamBackend]
+        registry.add('backend', StreamBackend)
diff --git a/mopidy/http/__init__.py b/mopidy/http/__init__.py
index 64cb88f9..25e2dd46 100644
--- a/mopidy/http/__init__.py
+++ b/mopidy/http/__init__.py
@@ -35,6 +35,6 @@ class Extension(ext.Extension):
         except ImportError as e:
             raise exceptions.ExtensionError('ws4py library not found', e)
 
-    def get_frontend_classes(self):
+    def setup(self, registry):
         from .actor import HttpFrontend
-        return [HttpFrontend]
+        registry.add('frontend', HttpFrontend)
diff --git a/mopidy/mpd/__init__.py b/mopidy/mpd/__init__.py
index 571d6455..77aaf83f 100644
--- a/mopidy/mpd/__init__.py
+++ b/mopidy/mpd/__init__.py
@@ -29,6 +29,6 @@ class Extension(ext.Extension):
     def validate_environment(self):
         pass
 
-    def get_frontend_classes(self):
+    def setup(self, registry):
         from .actor import MpdFrontend
-        return [MpdFrontend]
+        registry.add('frontend', MpdFrontend)