diff --git a/Database/MongoDB/Structured/Query.hs b/Database/MongoDB/Structured/Query.hs
--- a/Database/MongoDB/Structured/Query.hs
+++ b/Database/MongoDB/Structured/Query.hs
@@ -72,6 +72,7 @@
 import Database.MongoDB.Structured.Types
 import Database.MongoDB.Internal.Util
 import Data.Bson
+import Data.Maybe (fromJust)
 import Data.List (sortBy, groupBy)
 import Data.Functor
 import Data.Word
@@ -167,10 +168,11 @@
   res <- M.findOne . unStructuredQuery $ q
   return $ res >>= fromBSON
 
--- | Same as 'findOne' but throws 'DocNotFound' if none match.
+-- | Same as 'findOne' but throws 'DocNotFound' if none match. Error
+-- is thrown if the document cannot e transformed.
 fetch :: (MonadIO m, Functor m, Structured a)
-     => StructuredQuery -> Action m (Maybe a)
-fetch q = fromBSON <$> (M.fetch . unStructuredQuery $ q)
+     => StructuredQuery -> Action m a
+fetch q = (fromJust . fromBSON) <$> (M.fetch . unStructuredQuery $ q)
 
 -- | Count number of documents satisfying query.
 count :: (MonadIO' m) => StructuredQuery -> Action m Int
diff --git a/structured-mongoDB.cabal b/structured-mongoDB.cabal
--- a/structured-mongoDB.cabal
+++ b/structured-mongoDB.cabal
@@ -1,5 +1,5 @@
 Name:           structured-mongoDB
-Version:        0.2
+Version:        0.3
 build-type:     Simple
 License:        GPL
 License-File:   LICENSE