diff --git a/beets/library.py b/beets/library.py
index bd88136f1..139cdfec0 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -259,7 +259,7 @@ class LibModel(dbcore.Model):
     """Shared concrete functionality for Items and Albums.
     """
 
-    format_config_key = None
+    _format_config_key = None
     """Config key that specifies how an instance should be formatted.
     """
 
@@ -282,7 +282,7 @@ class LibModel(dbcore.Model):
 
     def __format__(self, spec):
         if not spec:
-            spec = beets.config[self.format_config_key].get(unicode)
+            spec = beets.config[self._format_config_key].get(unicode)
         result = self.evaluate_template(spec)
         if isinstance(spec, bytes):
             # if spec is a byte string then we must return a one as well
@@ -444,7 +444,7 @@ class Item(LibModel):
 
     _sorts = {'artist': SmartArtistSort}
 
-    format_config_key = 'format_item'
+    _format_config_key = 'format_item'
 
     @classmethod
     def _getters(cls):
@@ -877,7 +877,7 @@ class Album(LibModel):
     """List of keys that are set on an album's items.
     """
 
-    format_config_key = 'format_album'
+    _format_config_key = 'format_album'
 
     @classmethod
     def _getters(cls):
diff --git a/beets/ui/__init__.py b/beets/ui/__init__.py
index 85c5e4824..335129af2 100644
--- a/beets/ui/__init__.py
+++ b/beets/ui/__init__.py
@@ -637,7 +637,7 @@ class CommonOptionsParser(optparse.OptionParser, object):
         value = fmt or value and unicode(value) or ''
         parser.values.format = value
         if target:
-            config[target.format_config_key].set(value)
+            config[target._format_config_key].set(value)
         else:
             if self._album_flags:
                 if parser.values.album:
@@ -648,10 +648,10 @@ class CommonOptionsParser(optparse.OptionParser, object):
                         target = library.Album
                     else:
                         target = library.Item
-                config[target.format_config_key].set(value)
+                config[target._format_config_key].set(value)
             else:
-                config[library.Item.format_config_key].set(value)
-                config[library.Album.format_config_key].set(value)
+                config[library.Item._format_config_key].set(value)
+                config[library.Album._format_config_key].set(value)
 
     def add_path_option(self, flags=('-p', '--path')):
         """Add a -p/--path option to display the path instead of the default