diff --git a/addons/account_asset/account_asset.py b/addons/account_asset/account_asset.py
index b335063b758..29df81b5279 100644
--- a/addons/account_asset/account_asset.py
+++ b/addons/account_asset/account_asset.py
@@ -25,6 +25,7 @@ from dateutil.relativedelta import relativedelta
 
 from openerp.osv import fields, osv
 import openerp.addons.decimal_precision as dp
+from tools.translate import _
 
 class account_asset_category(osv.osv):
     _name = 'account.asset.category'
@@ -75,6 +76,12 @@ class account_asset_asset(osv.osv):
     _name = 'account.asset.asset'
     _description = 'Asset'
 
+    def unlink(self, cr, uid, ids, context=None):
+        for asset in self.browse(cr, uid, ids, context=context):
+            if asset.account_move_line_ids: 
+                raise osv.except_osv(_('Error!'), _('You cannot delete an asset that contains posted depreciation lines.'))
+        return super(account_account, self).unlink(cr, uid, ids, context=context)
+
     def _get_period(self, cr, uid, context=None):
         periods = self.pool.get('account.period').find(cr, uid)
         if periods:
@@ -369,7 +376,7 @@ class account_asset_depreciation_line(osv.osv):
     _columns = {
         'name': fields.char('Depreciation Name', size=64, required=True, select=1),
         'sequence': fields.integer('Sequence', required=True),
-        'asset_id': fields.many2one('account.asset.asset', 'Asset', required=True),
+        'asset_id': fields.many2one('account.asset.asset', 'Asset', required=True, ondelete='cascade'),
         'parent_state': fields.related('asset_id', 'state', type='char', string='State of Asset'),
         'amount': fields.float('Current Depreciation', digits_compute=dp.get_precision('Account'), required=True),
         'remaining_value': fields.float('Next Period Depreciation', digits_compute=dp.get_precision('Account'),required=True),
@@ -454,7 +461,7 @@ account_asset_depreciation_line()
 class account_move_line(osv.osv):
     _inherit = 'account.move.line'
     _columns = {
-        'asset_id': fields.many2one('account.asset.asset', 'Asset'),
+        'asset_id': fields.many2one('account.asset.asset', 'Asset', ondelete="restrict"),
         'entry_ids': fields.one2many('account.move.line', 'asset_id', 'Entries', readonly=True, states={'draft':[('readonly',False)]}),
 
     }