diff --git a/.gitignore b/.gitignore
index a3d640f..edd4559 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,5 @@
 .*
 !.gitignore
 \#*
-*.info
\ No newline at end of file
+*.info
+datok
\ No newline at end of file
diff --git a/datokenizer.go b/datokenizer.go
index 9f8079b..805b8df 100644
--- a/datokenizer.go
+++ b/datokenizer.go
@@ -74,6 +74,7 @@
 // of the tokenizer.
 type Tokenizer struct {
 	sigmaRev    map[int]rune
+	sigmaMCS    map[int]string
 	arcCount    int
 	sigmaCount  int
 	transitions []map[int]*edge
@@ -137,6 +138,7 @@
 
 	tok := &Tokenizer{
 		sigmaRev: make(map[int]rune),
+		sigmaMCS: make(map[int]string),
 		epsilon:  -1,
 		unknown:  -1,
 		identity: -1,
@@ -352,10 +354,13 @@
 								")")
 						return nil
 					}
-
 				} else if inSym == tok.epsilon {
 					log.Println("General epsilon transitions are not supported")
 					return nil
+				} else if tok.sigmaMCS[inSym] != "" {
+					log.Fatalln("Non supported character", tok.sigmaMCS[inSym])
+				} else if tok.sigmaMCS[outSym] != "" {
+					log.Fatalln("Non supported character", tok.sigmaMCS[outSym])
 				}
 
 				// Create an edge based on the collected information
@@ -451,8 +456,8 @@
 						}
 					default:
 						{
-							log.Println("MCS not supported: " + line)
-							return nil
+							// MCS not supported
+							tok.sigmaMCS[number] = line
 						}
 					}
 					continue
@@ -464,8 +469,9 @@
 						return nil
 					}
 					if len(line) != 1 {
-						log.Println("MCS not supported:" + line)
-						return nil
+						// MCS not supported
+						tok.sigmaMCS[number] = line
+						continue
 					}
 					symbol = rune('\n')
 				}
@@ -474,7 +480,7 @@
 			}
 		}
 	}
-
+	tok.sigmaMCS = nil
 	return tok
 }
 
diff --git a/datokenizer_test.go b/datokenizer_test.go
index ef6ccb4..ffee353 100644
--- a/datokenizer_test.go
+++ b/datokenizer_test.go
@@ -136,6 +136,28 @@
 	assert.True(tmatch(dat2, "wald gehen"))
 }
 
+func TestIgnorableMCS(t *testing.T) {
+	assert := assert.New(t)
+	// File has MCS in sigma but not in net
+	tok := LoadFomaFile("testdata/ignorable_mcs.fst")
+	assert.NotNil(tok)
+	dat := tok.ToDoubleArray()
+	assert.NotNil(dat)
+
+	b := make([]byte, 0, 2048)
+	w := bytes.NewBuffer(b)
+	var tokens []string
+
+	// Is only unambigous when transducing strictly greedy!
+	assert.True(dat.Transduce(strings.NewReader("ab<ab>"), w))
+	tokens = strings.Split(w.String(), "\n")
+	assert.Equal("a\nb\n<ab>\n", w.String())
+	assert.Equal("a", tokens[0])
+	assert.Equal("b", tokens[1])
+	assert.Equal("<ab>", tokens[2])
+	assert.Equal(4, len(tokens))
+}
+
 func TestFullTokenizer(t *testing.T) {
 	assert := assert.New(t)
 	dat := LoadDatokFile("testdata/tokenizer.datok")
diff --git a/testdata/ignorable_mcs.fst b/testdata/ignorable_mcs.fst
new file mode 100644
index 0000000..c114635
--- /dev/null
+++ b/testdata/ignorable_mcs.fst
Binary files differ