diff --git a/beets/dbcore/db.py b/beets/dbcore/db.py
index 524ee0b00..409ecc9af 100755
--- a/beets/dbcore/db.py
+++ b/beets/dbcore/db.py
@@ -56,10 +56,11 @@ class FormattedMapping(Mapping):
     are replaced.
     """
 
-    def __init__(self, model, for_path=False):
+    def __init__(self, model, for_path=False, compute_keys=True):
         self.for_path = for_path
         self.model = model
-        self.model_keys = model.keys(True)
+        if compute_keys:
+            self.model_keys = model.keys(True)
 
     def __getitem__(self, key):
         if key in self.model_keys:
diff --git a/beets/library.py b/beets/library.py
index 5e6a0ec8a..f9b5a2ab4 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -375,9 +375,10 @@ class FormattedItemMapping(dbcore.db.FormattedMapping):
     """
 
     def __init__(self, item, for_path=False):
-        super(FormattedItemMapping, self).__init__(item, for_path)
         # We treat album and item keys specially here,
         # so exclude transitive album keys from the model's keys.
+        super(FormattedItemMapping, self).__init__(item, for_path,
+                                                   compute_keys=False)
         self.model_keys = item.keys(computed=True, with_album=False)
         self.item = item