diff --git a/addons/account_asset/account_asset.py b/addons/account_asset/account_asset.py
index 4220fe0df1e..0160fc991a4 100644
--- a/addons/account_asset/account_asset.py
+++ b/addons/account_asset/account_asset.py
@@ -314,6 +314,8 @@ class account_asset_depreciation_line(osv.osv):
         currency_obj = self.pool.get('res.currency')
         for line in self.browse(cr, uid, ids, context=context):
             depreciation_date = time.strftime('%Y-%m-%d')
+            if line.asset_id.prorata:
+                depreciation_date = line.asset_id.purchase_date
             period_ids = period_obj.find(cr, uid, depreciation_date, context=context)
             company_currency = line.asset_id.company_id.currency_id.id
             current_currency = line.asset_id.currency_id.id