diff --git a/haskore.cabal b/haskore.cabal
--- a/haskore.cabal
+++ b/haskore.cabal
@@ -1,5 +1,5 @@
 Name:           haskore
-Version:        0.0.6
+Version:        0.0.7
 License:        GPL
 License-File:   LICENSE
 Author:         Paul Hudak <paul.hudak@yale.edu>, Henning Thielemann
@@ -31,7 +31,7 @@
 Source-Repository this
   type:     darcs
   location: http://darcs.haskell.org/haskore/
-  tag:      0.0.6
+  tag:      0.0.7
 
 Flag splitBase
   description: Choose the new smaller, split-up base package.
@@ -46,7 +46,7 @@
     midi >=0.1.1 && <0.2,
     markov-chain >=0.0.1 && <0.1,
     non-negative >=0.0.1 && <0.1,
-    data-accessor >=0.1 && <0.2,
+    data-accessor >=0.2 && <0.3,
     transformers >=0.0.1 && <0.2,
     haskell-src >=1.0 && <1.1,
     parsec >=2.1 && <2.2,
diff --git a/src/Haskore/General/Map.hs b/src/Haskore/General/Map.hs
--- a/src/Haskore/General/Map.hs
+++ b/src/Haskore/General/Map.hs
@@ -51,14 +51,14 @@
   We replace them by more usable ones here.
 -}
 
-lookup :: (Monad m, Ord k) => Map k a -> k -> m a
+lookup :: Ord k => Map k a -> k -> Maybe a
 lookup = flip Map.lookup
 
 findWithDefault :: Ord k => Map k a -> a -> k -> a
 findWithDefault dict deflt key =
    Map.findWithDefault deflt key dict
 
-lookupIndex :: (Monad m, Ord k) => Map k a -> k -> m Int
+lookupIndex :: Ord k => Map k a -> k -> Maybe Int
 lookupIndex = flip Map.lookupIndex
 
 findIndex :: Ord k => Map k a -> k -> Int