diff --git a/python/obitools3/dms/view/view.pyx b/python/obitools3/dms/view/view.pyx
index 58a8c3d..802e639 100755
--- a/python/obitools3/dms/view/view.pyx
+++ b/python/obitools3/dms/view/view.pyx
@@ -799,7 +799,8 @@ cdef class Line :
  
  
     def keys(self):
-        return self._view.keys()
+        cdef bytes key
+        return [key for key in self._view.keys()]
  
  
     def __contains__(self, object column_name):