diff --git a/README.rst b/README.rst
index ff6d16d..56bb13c 100644
--- a/README.rst
+++ b/README.rst
@@ -52,8 +52,7 @@ types:
            # insert your handlers here
        ])
 
-       content.add_transcoder(application, transcoders.JSONTranscoder(),
-                              'application/json')
+       content.add_transcoder(application, transcoders.JSONTranscoder())
 
        return application
 
diff --git a/examples.py b/examples.py
index 5e07470..bef1f27 100644
--- a/examples.py
+++ b/examples.py
@@ -18,10 +18,8 @@ def make_application(**settings):
     application = web.Application([web.url(r'/', SimpleHandler)], **settings)
     content.set_default_content_type(application, 'application/json',
                                      encoding='utf-8')
-    content.add_transcoder(application, transcoders.MsgPackTranscoder(),
-                           content_type='application/msgpack')
-    content.add_transcoder(application, transcoders.JSONTranscoder(),
-                           content_type='application/json')
+    content.add_transcoder(application, transcoders.MsgPackTranscoder())
+    content.add_transcoder(application, transcoders.JSONTranscoder())
     return application
 
 
diff --git a/sprockets/mixins/mediatype/content.py b/sprockets/mixins/mediatype/content.py
index 1633dae..b0e69a2 100644
--- a/sprockets/mixins/mediatype/content.py
+++ b/sprockets/mixins/mediatype/content.py
@@ -132,8 +132,7 @@ def add_binary_content_type(application, content_type, pack, unpack):
 
     """
     add_transcoder(application,
-                   handlers.BinaryContentHandler(content_type, pack, unpack),
-                   content_type)
+                   handlers.BinaryContentHandler(content_type, pack, unpack))
 
 
 def add_text_content_type(application, content_type, default_encoding,
@@ -158,22 +157,28 @@ def add_text_content_type(application, content_type, default_encoding,
     normalized = str(parsed)
     add_transcoder(application,
                    handlers.TextContentHandler(normalized, dumps, loads,
-                                               default_encoding),
-                   normalized)
+                                               default_encoding))
 
 
-def add_transcoder(application, transcoder, content_type):
+def add_transcoder(application, transcoder, content_type=None):
     """
     Register a transcoder for a specific content type.
 
     :param tornado.web.Application application: the application to modify
     :param transcoder: object that translates between :class:`bytes` and
         :class:`object` instances
-    :param str content_type: the content type to add
+    :param str content_type: the content type to add.  If this is
+        unspecified or :data:`None`, then the transcoder's ``content_type``
+        attribute is used.
 
     The `transcoder` instance is required to implement the following
     simple protocol:
 
+    .. attribute:: transcoder.content_type
+
+       :class:`str` that identifies the MIME type that the transcoder
+       implements.
+
     .. method:: transcoder.to_bytes(inst_data, encoding=None) -> bytes
 
        :param object inst_data: the object to encode
@@ -188,7 +193,7 @@ def add_transcoder(application, transcoder, content_type):
 
     """
     settings = ContentSettings.from_application(application)
-    settings[content_type] = transcoder
+    settings[content_type or transcoder.content_type] = transcoder
 
 
 def set_default_content_type(application, content_type, encoding=None):