diff --git a/mopidy/core/library.py b/mopidy/core/library.py
index ca0a159d..e6da95f1 100644
--- a/mopidy/core/library.py
+++ b/mopidy/core/library.py
@@ -189,13 +189,8 @@ class LibraryController(object):
         .. deprecated:: 1.0
             The ``uri`` argument. Use ``uris`` instead.
         """
-        none_set = uri is None and uris is None
-        both_set = uri is not None and uris is not None
-
-        if none_set or both_set:
-            raise ValueError("One of 'uri' or 'uris' must be set")
-
-        # TODO: validation.one_of(*args)?
+        if sum(o is not None for o in [uri, uris]) != 1:
+            raise ValueError('Exactly one of "uri" or "uris" must be set')
 
         uris is None or validation.check_uris(uris)
         uri is None or validation.check_uri(uri)
diff --git a/mopidy/core/playback.py b/mopidy/core/playback.py
index 2b1bbbc3..3605db0f 100644
--- a/mopidy/core/playback.py
+++ b/mopidy/core/playback.py
@@ -277,9 +277,12 @@ class PlaybackController(object):
         :param tlid: TLID of the track to play
         :type tlid: :class:`int` or :class:`None`
         """
+        if sum(o is not None for o in [tl_track, tlid]) > 1:
+            raise ValueError('At most one of "tl_track" and "tlid" may be set')
+
         tl_track is None or validation.check_instance(tl_track, models.TlTrack)
         tlid is None or validation.check_integer(tlid, min=0)
-        # TODO: check one of or none for args
+
         if tl_track:
             deprecation.warn('core.playback.play:tl_track_kwarg', pending=True)
 
diff --git a/mopidy/core/tracklist.py b/mopidy/core/tracklist.py
index dfcd503a..692762ef 100644
--- a/mopidy/core/tracklist.py
+++ b/mopidy/core/tracklist.py
@@ -406,10 +406,9 @@ class TracklistController(object):
         .. deprecated:: 1.0
             The ``tracks`` and ``uri`` arguments. Use ``uris``.
         """
-        assert tracks is not None or uri is not None or uris is not None, \
-            'tracks, uri or uris must be provided'
-        # TODO: check that only one of tracks uri and uris is set...
-        # TODO: can at_position be negative?
+        if sum(o is not None for o in [tracks, uri, uris]) != 1:
+            raise ValueError(
+                'Exactly one of "tracks", "uri" or "uris" must be set')
 
         tracks is None or validation.check_instances(tracks, Track)
         uri is None or validation.check_uri(uri)