diff --git a/docs/conf.py b/docs/conf.py
index 7f111014..1e9f9cb2 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -32,7 +32,8 @@ class Mock(object):
     def __getattr__(self, name):
         if name in ('__file__', '__path__'):
             return '/dev/null'
-        elif name[0] == name[0].upper() and not name.startswith('MIXER_TRACK'):
+        elif (name[0] == name[0].upper()
+                and not name.startswith('MIXER_TRACK_')):
             return type(name, (), {})
         else:
             return Mock()