diff --git a/bin/osv/fields.py b/bin/osv/fields.py
index 72df0e925ad..7cac40f2ec8 100644
--- a/bin/osv/fields.py
+++ b/bin/osv/fields.py
@@ -63,7 +63,13 @@ class _column(object):
     _symbol_set = (_symbol_c, _symbol_f)
     _symbol_get = None
 
-    def __init__(self, string='unknown', required=False, readonly=False, domain=None, context=None, states=None, priority=0, change_default=False, size=None, ondelete="set null", translate=False, select=False, **args):
+    def __init__(self, string='unknown', required=False, readonly=False, domain=None, context=None, states=None, priority=0, change_default=False, size=None, ondelete="set null", translate=False, select=False, manual=False, **args):
+        """
+
+        The 'manual' kayword argument specify if the field is a custom one. It
+        correspond to the 'state' column in ir_model_fields.
+
+        """
         if domain is None:
             domain = []
         if context is None:
@@ -84,6 +90,7 @@ class _column(object):
         self.read = False
         self.view_load = 0
         self.select = select
+        self.manual = manual
         self.selectable = True
         self.group_operator = args.get('group_operator', False)
         for a in args:
diff --git a/bin/osv/orm.py b/bin/osv/orm.py
index 91574e7fa6a..337125df29f 100644
--- a/bin/osv/orm.py
+++ b/bin/osv/orm.py
@@ -2826,6 +2826,7 @@ class orm(orm_template):
                     'size': field['size'],
                     'ondelete': field['on_delete'],
                     'translate': (field['translate']),
+                    'manual': True,
                     #'select': int(field['select_level'])
                 }
 
diff --git a/bin/osv/osv.py b/bin/osv/osv.py
index 138e8c8daab..0d8cad9e4e5 100644
--- a/bin/osv/osv.py
+++ b/bin/osv/osv.py
@@ -298,6 +298,11 @@ class osv_memory(osv_base, orm.orm_memory):
                 nattr = {}
                 for s in ('_columns', '_defaults'):
                     new = copy.copy(getattr(pool.get(parent_name), s))
+                    if s == '_columns':
+                        # Don't _inherit custom fields.
+                        for c in new.keys():
+                            if new[c].manual:
+                                del new[c]
                     if hasattr(new, 'update'):
                         new.update(cls.__dict__.get(s, {}))
                     else:
@@ -332,6 +337,11 @@ class osv(osv_base, orm.orm):
                 nattr = {}
                 for s in ('_columns', '_defaults', '_inherits', '_constraints', '_sql_constraints'):
                     new = copy.copy(getattr(pool.get(parent_name), s))
+                    if s == '_columns':
+                        # Don't _inherit custom fields.
+                        for c in new.keys():
+                            if new[c].manual:
+                                del new[c]
                     if hasattr(new, 'update'):
                         new.update(cls.__dict__.get(s, {}))
                     else: