Index: lattice/src/LatticeExpand.cc
===================================================================
--- lattice/src/LatticeExpand.cc	(.../1.5.1/lattice/src/LatticeExpand.cc)	(revision 345)
+++ lattice/src/LatticeExpand.cc	(.../trunk/lattice/src/LatticeExpand.cc)	(working copy)
@@ -1448,7 +1448,8 @@
 	}
     }
 
-    LatticeTransition newTrans(transProb, oldTrans->flags);
+    // BUG FIX: Old transition was being replaced by new, but new discarded old weight!
+    LatticeTransition newTrans(transProb + oldTrans->weight, oldTrans->flags);
     insertTrans(newIndex, *newIndex2, newTrans, 0);
 
     // restore full context