diff --git a/openerp/api.py b/openerp/api.py
index da9e62f1549..d13bcd57567 100644
--- a/openerp/api.py
+++ b/openerp/api.py
@@ -2,7 +2,7 @@
 ##############################################################################
 #
 #    OpenERP, Open Source Management Solution
-#    Copyright (C) 2013 OpenERP (<http://www.openerp.com>).
+#    Copyright (C) 2013-2014 OpenERP (<http://www.openerp.com>).
 #
 #    This program is free software: you can redistribute it and/or modify
 #    it under the terms of the GNU Affero General Public License as
@@ -717,7 +717,7 @@ class Environment(object):
         self.cache = defaultdict(dict)      # {field: {id: value, ...}, ...}
         self.prefetch = defaultdict(set)    # {model_name: set(id), ...}
         self.computed = defaultdict(set)    # {field: set(id), ...}
-        self.dirty = set()                  # set(record)
+        self.dirty = defaultdict(set)       # {record: set(field_name), ...}
         self.all = envs
         envs.add(self)
         return self
diff --git a/openerp/fields.py b/openerp/fields.py
index 43b63f84b13..69869db6e4e 100644
--- a/openerp/fields.py
+++ b/openerp/fields.py
@@ -791,7 +791,7 @@ class Field(object):
             if env.in_onchange:
                 for invf in self.inverse_fields:
                     invf._update(value, record)
-                record._dirty = True
+                record._set_dirty_by(self.name)
 
             # determine more dependent fields, and invalidate them
             if self.relational:
@@ -1578,7 +1578,8 @@ class _RelationalMulti(_Relational):
         # add new and existing records
         for record in value:
             if not record.id or record._dirty:
-                values = dict((k, v) for k, v in record._cache.iteritems() if k in fnames)
+                dirty_fields = record.env.dirty[record]
+                values = dict((k, v) for k, v in record._cache.iteritems() if k in fnames and k in dirty_fields)
                 values = record._convert_to_write(values)
                 if not record.id:
                     result.append((0, 0, values))
diff --git a/openerp/models.py b/openerp/models.py
index df46fce4d5d..d44ced403a4 100644
--- a/openerp/models.py
+++ b/openerp/models.py
@@ -5320,15 +5320,12 @@ class BaseModel(object):
     def _dirty(self):
         """ Return whether any record in `self` is dirty. """
         dirty = self.env.dirty
-        return any(record in dirty for record in self)
+        return any(bool(dirty.get(record)) for record in self)
 
-    @_dirty.setter
-    def _dirty(self, value):
-        """ Mark the records in `self` as dirty. """
-        if value:
-            map(self.env.dirty.add, self)
-        else:
-            map(self.env.dirty.discard, self)
+    def _set_dirty_by(self, field_name):
+        dirty = self.env.dirty
+        for record in self:
+            dirty[record].add(field_name)
 
     #
     # "Dunder" methods