diff --git a/python/obitools3/dms/view/view.pyx b/python/obitools3/dms/view/view.pyx
index 267f127..a9e1466 100644
--- a/python/obitools3/dms/view/view.pyx
+++ b/python/obitools3/dms/view/view.pyx
@@ -444,9 +444,12 @@ cdef class Line :
                 
         # TODO use functions in utils
         
+        #print(column_name, "value:", value, type(value))
+        
         if column_name_b not in self._view :
-            if value == None :
-                raise RollbackException("Trying to create a column from a None value (can't guess type)", self)
+            if value is None :
+                return # TODO discuss. This means that columns aren't created until an identifiable type is found
+                #raise RollbackException("Trying to create a column from a None value (can't guess type)", self)
             value_type = type(value)
             if value_type == int :
                 value_obitype = OBI_INT
@@ -636,13 +639,15 @@ cdef class Line_selection(list):
 
 
 class RollbackException(Exception):
-    def __init__(self, message, View view):
+    def __init__(self, message, *views):
         super(RollbackException, self).__init__(message)
-        if obi_rollback_view(<Obiview_p>(view.pointer())) < 0 :
-            raise Exception("Error rollbacking view")
-        if view.active() :
-            view._dms.unregister(view)
-            OBIWrapper.close(view)
+        for i in range(len(views)):
+            view = <View>(views[i])
+            if obi_rollback_view(<Obiview_p>(view.pointer())) < 0 :
+                raise Exception("Error rollbacking view")
+            if view.active() :
+                view._dms.unregister(view)
+                OBIWrapper.close(view)
 
 
 class CantGuessTypeException(Exception):