1 files changed, 6 insertions, 0 deletions
diff --git a/decoder/tree2string_translator.cc b/decoder/tree2string_translator.cc
index 09eca147..7bc49132 100644
--- a/decoder/tree2string_translator.cc
+++ b/decoder/tree2string_translator.cc
@@ -167,6 +167,12 @@ struct Tree2StringTranslatorImpl {
     //cerr << "Goal node: " << goal << endl;
     hg.TopologicallySortNodesAndEdges(goal);
     hg.Reweight(weights);
+
+    // there might be nodes that cannot be derived
+    // the following takes care of them
+    vector<bool> prune(hg.edges_.size(), false);
+    hg.PruneEdges(prune, true);
+
     //hg.PrintGraphviz();
     minus_lm_forest->swap(hg);
     return true;