--- a/Implab/Automaton/MapAlphabet.cs	Wed Feb 24 20:12:52 2016 +0300
+++ b/Implab/Automaton/MapAlphabet.cs	Thu Feb 25 02:11:13 2016 +0300
@@ -5,11 +5,14 @@
 namespace Implab.Automaton {
     public class MapAlphabet<T> : IAlphabetBuilder<T> {
         readonly Dictionary<T,int> m_map;
-        int m_nextCls;
+        int m_nextCls = 1;
+
+        public MapAlphabet() {
+            m_map = new Dictionary<T, int>();
+        }
 
         public MapAlphabet(IEqualityComparer<T> comparer) {
             m_map = new Dictionary<T, int>(comparer);
-            m_nextCls = 1;
         }
 
         #region IAlphabetBuilder implementation
@@ -71,6 +74,9 @@
             var map = new int[rmap.Length];
 
             foreach (var cls in classes) {
+                if (cls.Contains(DFAConst.UNCLASSIFIED_INPUT))
+                    continue;
+                
                 var symbols = new List<T>();
                 foreach (var id in cls) {
                     if (id < 0 || id >= rmap.Length)