diff --git a/euler-tour-tree.cabal b/euler-tour-tree.cabal
--- a/euler-tour-tree.cabal
+++ b/euler-tour-tree.cabal
@@ -1,5 +1,5 @@
 name:                euler-tour-tree
-version:             0.1.0.0
+version:             0.1.0.1
 synopsis:            Euler tour trees
 -- description:         Cf README file
 homepage:            https://github.com/k0ral/euler-tour-tree
diff --git a/src/Data/EulerTourTree.hs b/src/Data/EulerTourTree.hs
--- a/src/Data/EulerTourTree.hs
+++ b/src/Data/EulerTourTree.hs
@@ -30,21 +30,19 @@
   ) where
 
 -- {{{ Imports
-import           Control.Applicative             hiding (empty)
-import           Control.Applicative.Combinators
-import           Control.Monad
-import           Control.Monad.State.Lazy
-import           Control.Monad.Trans.Maybe
+import           Control.Applicative             ((<|>))
+import           Control.Applicative.Combinators (endBy)
+import           Control.Monad                   (MonadPlus (..), guard)
+import           Control.Monad.State.Lazy        (MonadState (..), evalStateT)
 import           Data.FingerTree                 hiding (empty, null, singleton)
 import qualified Data.FingerTree                 as FingerTree
-import           Data.Foldable
-import           Data.List.Unique
-import           Data.Maybe
+import           Data.Foldable                   (Foldable (..))
+import           Data.List.Unique                (allUnique)
+import           Data.Maybe                      (fromMaybe)
 import           Data.Monoid
 import           Data.Set                        (Set)
 import qualified Data.Set                        as Set
-import           Data.Tree
-import           Debug.Trace
+import           Data.Tree                       (Tree (..))
 -- }}}
 
 searchM :: MonadPlus m => Measured v a => (v -> v -> Bool) -> FingerTree v a -> m (FingerTree v a, a, FingerTree v a)
@@ -214,7 +212,7 @@
 
 -- | /O(log n)/ Rotate @tree@ such that @node@ is the new root.
 --
--- Return 'Nothing' if @node@ isn't found in @tree@.
+-- Fail if @node@ isn't found in @tree@.
 reroot :: MonadPlus m
        => Ord node
        => node                 -- ^ Denoted by @node@