diff --git a/src/obitools/sequenceencoder/__init__.py b/src/obitools/sequenceencoder/__init__.py
index 89a8a59..4838829 100644
--- a/src/obitools/sequenceencoder/__init__.py
+++ b/src/obitools/sequenceencoder/__init__.py
@@ -11,6 +11,7 @@ class DNAComplementEncoder(SequenceEncoder):
            '-': '-'}
 
     _info={'complemented':True}
+    _eval={'complemented':True}
 
     @staticmethod
     def _encode(seq,position=slice(None, None, -1)):
@@ -43,6 +44,7 @@ class SeqFragmentEncoder(SequenceEncoder):
         assert begin < end and begin >=0
         self._limits = slice(begin,end)
         self._info = {'cut' : [begin,end,1]}
+        self._eval = {'cut' : True}
         self._len = end - begin + 1
         
     def _check(self,seq):