diff --git a/Data/Graph/Libgraph/AlgoDebug.hs b/Data/Graph/Libgraph/AlgoDebug.hs
--- a/Data/Graph/Libgraph/AlgoDebug.hs
+++ b/Data/Graph/Libgraph/AlgoDebug.hs
@@ -2,6 +2,8 @@
 import Data.Graph.Libgraph.Core
 import Data.Graph.Libgraph.Dagify(collapse,remove)
 import Prelude hiding (Right)
+import Data.List(find)
+import Data.Maybe(isJust)
 
 data Judgement = Right | Wrong | Unassessed | Assisted String deriving (Eq,Show,Ord)
 
@@ -14,7 +16,26 @@
            => (v -> Judgement) -> ([v]->v) -> Graph v a -> [v]
 findFaulty isWrong merge = (findFaulty_dag isWrong) . (collapse merge) . remove
 
+next_step :: Eq v => Graph v a -> (v -> Judgement) -> v
+next_step tree j = case go r of 
+  Just v  -> v
+  Nothing -> r -- no defect?
+  where
+  r = root tree
+  go v | v == r       = findJust (map go (succs tree v))
+       | j v == Right = Nothing                -- v is right; don't examine (grand)children
+       | j v == Wrong = case findJust (map go (succs tree v)) of
+                          Nothing  -> (Just v) -- v is a faulty node
+                          (Just w) -> (Just w) -- found next node w in (grand)children of v
+       | otherwise    = Just v                 -- v is an unassed node
+  findJust mvs = case (find (isJust) mvs) of Just justv -> justv; Nothing -> Nothing
 
+{- A more efficient next_step implementation; that starts from the
+   current computation statement. The problem with this implementation
+   is that it can get "stuck" in trees with nodes that already have some
+   judged nodes (e.g. due to free exploration or using property-assisted
+   algorithmic debugging.)
+
 next_step :: Eq v => Graph v a -> (v -> Judgement) -> v -> v
 next_step tree j v 
   | j v == Wrong || v == root tree =
@@ -28,3 +49,4 @@
                       (w:_) -> next_step tree j w
 
   | otherwise = v -- j v is Unassessed or Assisted
+-}
diff --git a/libgraph.cabal b/libgraph.cabal
--- a/libgraph.cabal
+++ b/libgraph.cabal
@@ -1,5 +1,5 @@
 Name:           libgraph
-Version:        1.8
+Version:        1.9
 Homepage:       http://maartenfaddegon.nl
 Synopsis:       Store and manipulate data in a graph.
 Description:    A graph type, analysis of graphs and manipulation of graphs.