diff --git a/mopidy/models.py b/mopidy/models.py
index 4f8ae6fe..e936e22c 100644
--- a/mopidy/models.py
+++ b/mopidy/models.py
@@ -75,6 +75,11 @@ class String(Field):
         super(String, self).__init__(type=basestring, default=default)
 
 
+class Identifier(String):
+    def validate(self, value):
+        return intern(str(super(Identifier, self).validate(value)))
+
+
 class Integer(Field):
 
     """
@@ -290,7 +295,7 @@ class Ref(ImmutableObject):
     """
 
     #: The object URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     #: The object name. Read-only.
     name = String()
@@ -354,7 +359,7 @@ class Image(ImmutableObject):
     """
 
     #: The image URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     #: Optional width of the image or :class:`None`. Read-only.
     width = Integer(min=0)
@@ -375,13 +380,13 @@ class Artist(ImmutableObject):
     """
 
     #: The artist URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     #: The artist name. Read-only.
     name = String()
 
     #: The MusicBrainz ID of the artist. Read-only.
-    musicbrainz_id = String()
+    musicbrainz_id = Identifier()
 
 
 class Album(ImmutableObject):
@@ -406,7 +411,7 @@ class Album(ImmutableObject):
     """
 
     #: The album URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     #: The album name. Read-only.
     name = String()
@@ -424,7 +429,7 @@ class Album(ImmutableObject):
     date = String()  # TODO: add date type
 
     #: The MusicBrainz ID of the album. Read-only.
-    musicbrainz_id = String()
+    musicbrainz_id = Identifier()
 
     #: The album image URIs. Read-only.
     images = Collection(type=basestring, container=frozenset)
@@ -469,7 +474,7 @@ class Track(ImmutableObject):
     """
 
     #: The track URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     #: The track name. Read-only.
     name = String()
@@ -508,7 +513,7 @@ class Track(ImmutableObject):
     comment = String()
 
     #: The MusicBrainz ID of the track. Read-only.
-    musicbrainz_id = String()
+    musicbrainz_id = Identifier()
 
     #: Integer representing when the track was last modified. Exact meaning
     #: depends on source of track. For local files this is the modification
@@ -571,7 +576,7 @@ class Playlist(ImmutableObject):
     """
 
     #: The playlist URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     #: The playlist name. Read-only.
     name = String()
@@ -607,7 +612,7 @@ class SearchResult(ImmutableObject):
     """
 
     # The search result URI. Read-only.
-    uri = String()
+    uri = Identifier()
 
     # The tracks matching the search query. Read-only.
     tracks = Collection(type=Track, container=tuple)
diff --git a/tests/models/test_models.py b/tests/models/test_models.py
index 77383a6e..7e0d6bb9 100644
--- a/tests/models/test_models.py
+++ b/tests/models/test_models.py
@@ -86,7 +86,7 @@ class RefTest(unittest.TestCase):
 
     def test_repr_without_results(self):
         self.assertEqual(
-            "Ref(name=u'foo', type=u'artist', uri=u'uri')",
+            "Ref(name=u'foo', type=u'artist', uri='uri')",
             repr(Ref(uri='uri', name='foo', type='artist')))
 
     def test_serialize_without_results(self):
@@ -200,7 +200,7 @@ class ArtistTest(unittest.TestCase):
 
     def test_repr(self):
         self.assertEqual(
-            "Artist(name=u'name', uri=u'uri')",
+            "Artist(name=u'name', uri='uri')",
             repr(Artist(uri='uri', name='name')))
 
     def test_serialize(self):
@@ -365,12 +365,12 @@ class AlbumTest(unittest.TestCase):
 
     def test_repr_without_artists(self):
         self.assertEqual(
-            "Album(name=u'name', uri=u'uri')",
+            "Album(name=u'name', uri='uri')",
             repr(Album(uri='uri', name='name')))
 
     def test_repr_with_artists(self):
         self.assertEqual(
-            "Album(artists=[Artist(name=u'foo')], name=u'name', uri=u'uri')",
+            "Album(artists=[Artist(name=u'foo')], name=u'name', uri='uri')",
             repr(Album(uri='uri', name='name', artists=[Artist(name='foo')])))
 
     def test_serialize_without_artists(self):
@@ -609,12 +609,12 @@ class TrackTest(unittest.TestCase):
 
     def test_repr_without_artists(self):
         self.assertEqual(
-            "Track(name=u'name', uri=u'uri')",
+            "Track(name=u'name', uri='uri')",
             repr(Track(uri='uri', name='name')))
 
     def test_repr_with_artists(self):
         self.assertEqual(
-            "Track(artists=[Artist(name=u'foo')], name=u'name', uri=u'uri')",
+            "Track(artists=[Artist(name=u'foo')], name=u'name', uri='uri')",
             repr(Track(uri='uri', name='name', artists=[Artist(name='foo')])))
 
     def test_serialize_without_artists(self):
@@ -844,7 +844,7 @@ class TlTrackTest(unittest.TestCase):
 
     def test_repr(self):
         self.assertEqual(
-            "TlTrack(tlid=123, track=Track(uri=u'uri'))",
+            "TlTrack(tlid=123, track=Track(uri='uri'))",
             repr(TlTrack(tlid=123, track=Track(uri='uri'))))
 
     def test_serialize(self):
@@ -977,12 +977,12 @@ class PlaylistTest(unittest.TestCase):
 
     def test_repr_without_tracks(self):
         self.assertEqual(
-            "Playlist(name=u'name', uri=u'uri')",
+            "Playlist(name=u'name', uri='uri')",
             repr(Playlist(uri='uri', name='name')))
 
     def test_repr_with_tracks(self):
         self.assertEqual(
-            "Playlist(name=u'name', tracks=[Track(name=u'foo')], uri=u'uri')",
+            "Playlist(name=u'name', tracks=[Track(name=u'foo')], uri='uri')",
             repr(Playlist(uri='uri', name='name', tracks=[Track(name='foo')])))
 
     def test_serialize_without_tracks(self):
@@ -1114,7 +1114,7 @@ class SearchResultTest(unittest.TestCase):
 
     def test_repr_without_results(self):
         self.assertEqual(
-            "SearchResult(uri=u'uri')",
+            "SearchResult(uri='uri')",
             repr(SearchResult(uri='uri')))
 
     def test_serialize_without_results(self):