diff --git a/hierarchy.cabal b/hierarchy.cabal
--- a/hierarchy.cabal
+++ b/hierarchy.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 2596f3b56ac8cc1f0530263376774a0928ed672af04accda1fdf311d298fb764
+-- hash: 7748f3ca1f7405c760d01c22deb293079ce8eb68885b1e66a38b43b171c044eb
 
 name:           hierarchy
-version:        1.0.1
+version:        1.0.2
 synopsis:       Predicated traversal of generated trees
 description:    Predicated traversal of generated trees.
 category:       Data
@@ -32,7 +32,7 @@
       src
   build-depends:
       base >=4.7 && <4.12
-    , exceptions >=0.8 && <0.9
+    , exceptions >=0.10 && <0.12
     , free >=4.12 && <6
     , mmorph >=1.0 && <1.2
     , monad-control >=1.0 && <1.1
@@ -56,7 +56,7 @@
       base >=4.7 && <4.12
     , directory >=1.0
     , doctest >=0.8
-    , exceptions >=0.8 && <0.9
+    , exceptions >=0.10 && <0.12
     , filepath >=1.3
     , free >=4.12 && <6
     , mmorph >=1.0 && <1.2
diff --git a/src/Hierarchy.hs b/src/Hierarchy.hs
--- a/src/Hierarchy.hs
+++ b/src/Hierarchy.hs
@@ -8,7 +8,7 @@
 import Control.Cond
 
 -- | A 'TreeT' is a tree of values, where the (possible) branches are
---   'ListT's over some Monad 'm'.
+--   represented by some MonadPlus 'm'.
 type TreeT m = CofreeT Maybe m
 
 -- | Turn a list into a series of possibilities:
@@ -21,7 +21,7 @@
 descend (CofreeT t) = t >>= \(a :< mp) -> pure (a, mp)
 {-# INLINE descend #-}
 
--- | Perform a depth-first traversal of a 'TreeT', yielding a 'ListT' of its
+-- | Perform a depth-first traversal of a 'TreeT', yielding each of its
 --   contents. Note that breadth-first traversals cannot offer static memory
 --   guarantees, so they are not provided by this module.
 walk :: MonadPlus m => TreeT m a -> m a
@@ -44,7 +44,7 @@
 --         when (path @`elem@` [".@/@.git", ".@/@dist", ".@/@result"])
 --             prune  -- ignore these, and don't recurse into them
 --         guard_ (".hs" @`isInfixOf@`)  -- implicitly references 'path'
--- runEffect $ for (runListT (walk files)) $ liftIO . print
+-- forM_ (walk files) $ liftIO . print
 -- @
 winnow :: MonadPlus m => TreeT m a -> CondT a m () -> TreeT m a
 winnow (CofreeT t) p = CofreeT $ t >>= \(a :< mst) -> do