diff --git a/docs/changelog.rst b/docs/changelog.rst
index 34654d57..18c45b79 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -16,6 +16,14 @@ Feature release.
   new API introuced in v0.18 is now required. Most extensions already use the
   new API location.
 
+**Extension support**
+
+- Removed the :class:`~mopidy.ext.Extension` methods that were deprecated in
+  0.18: :meth:`~mopidy.ext.Extension.get_backend_classes`,
+  :meth:`~mopidy.ext.Extension.get_frontend_classes`, and
+  :meth:`~mopidy.ext.Extension.register_gstreamer_elements`. Use
+  meth:`mopidy.ext.Extension.setup` instead, as most extensions already do.
+
 **MPD frontend**
 
 - Proper command tokenization for MPD requests. This replaces the old regex
diff --git a/mopidy/ext.py b/mopidy/ext.py
index 4887f295..01b3e70e 100644
--- a/mopidy/ext.py
+++ b/mopidy/ext.py
@@ -99,42 +99,6 @@ class Extension(object):
         :param registry: the extension registry
         :type registry: :class:`Registry`
         """
-        for backend_class in self.get_backend_classes():
-            registry.add('backend', backend_class)
-
-        for frontend_class in self.get_frontend_classes():
-            registry.add('frontend', frontend_class)
-
-        self.register_gstreamer_elements()
-
-    def get_frontend_classes(self):
-        """List of frontend actor classes
-
-        .. deprecated:: 0.18
-            Use :meth:`setup` instead.
-
-        :returns: list of :class:`pykka.Actor` subclasses
-        """
-        return []
-
-    def get_backend_classes(self):
-        """List of backend actor classes
-
-        .. deprecated:: 0.18
-            Use :meth:`setup` instead.
-
-        :returns: list of :class:`~mopidy.backend.Backend` subclasses
-        """
-        return []
-
-    def register_gstreamer_elements(self):
-        """Hook for registering custom GStreamer elements.
-
-        .. deprecated:: 0.18
-            Use :meth:`setup` instead.
-
-        :returns: :class:`None`
-        """
         pass
 
 
diff --git a/tests/test_ext.py b/tests/test_ext.py
index f6b0ccfe..5338c91d 100644
--- a/tests/test_ext.py
+++ b/tests/test_ext.py
@@ -27,12 +27,3 @@ class ExtensionTest(unittest.TestCase):
 
     def test_validate_environment_does_nothing_by_default(self):
         self.assertIsNone(self.ext.validate_environment())
-
-    def test_get_frontend_classes_returns_an_empty_list(self):
-        self.assertListEqual(self.ext.get_frontend_classes(), [])
-
-    def test_get_backend_classes_returns_an_empty_list(self):
-        self.assertListEqual(self.ext.get_backend_classes(), [])
-
-    def test_register_gstreamer_elements_does_nothing_by_default(self):
-        self.assertIsNone(self.ext.register_gstreamer_elements())