diff --git a/README.rst b/README.rst
index 79c3f58..b4039c3 100644
--- a/README.rst
+++ b/README.rst
@@ -97,7 +97,7 @@ Audio
 -  **aac** - ``audio/aac``
 -  **mid** - ``audio/midi``
 -  **mp3** - ``audio/mpeg``
--  **m4a** - ``audio/m4a``
+-  **m4a** - ``audio/mp4``
 -  **ogg** - ``audio/ogg``
 -  **flac** - ``audio/x-flac``
 -  **wav** - ``audio/x-wav``
diff --git a/filetype/types/audio.py b/filetype/types/audio.py
index 2907c61..3d1f20c 100644
--- a/filetype/types/audio.py
+++ b/filetype/types/audio.py
@@ -56,7 +56,7 @@ class M4a(Type):
     """
     Implements the M4A audio type matcher.
     """
-    MIME = 'audio/m4a'
+    MIME = 'audio/mp4'
     EXTENSION = 'm4a'
 
     def __init__(self):