diff --git a/addons/mrp_subproduct/mrp_subproduct.py b/addons/mrp_subproduct/mrp_subproduct.py
index e271e2bfb26..c40718280ce 100644
--- a/addons/mrp_subproduct/mrp_subproduct.py
+++ b/addons/mrp_subproduct/mrp_subproduct.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 ##############################################################################
-#    
+#
 #    OpenERP, Open Source Management Solution
 #    Copyright (C) 2004-2010 Tiny SPRL (<http://tiny.be>).
 #
@@ -15,7 +15,7 @@
 #    GNU Affero General Public License for more details.
 #
 #    You should have received a copy of the GNU Affero General Public License
-#    along with this program.  If not, see <http://www.gnu.org/licenses/>.     
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 ##############################################################################
 
@@ -35,7 +35,10 @@ class mrp_subproduct(osv.osv):
     _defaults={
         'subproduct_type': lambda *args: 'fixed'
     }
-    
+    _sql_constraints = [
+        ('_check_product_qty', 'CHECK (product_qty > 0)', 'Enter valid product quantity !'),
+    ]
+
     def onchange_product_id(self, cr, uid, ids, product_id,context={}):
         """ Changes UoM if product_id changes.
         @param product_id: Changed product_id
@@ -53,7 +56,7 @@ class mrp_bom(osv.osv):
     _name = 'mrp.bom'
     _description = 'Bill of Material'
     _inherit='mrp.bom'
-    
+
     _columns={
         'sub_products':fields.one2many('mrp.subproduct', 'bom_id', 'sub_products'),
     }
@@ -62,7 +65,7 @@ mrp_bom()
 class mrp_production(osv.osv):
     _name = 'mrp.production'
     _description = 'Production'
-    _inherit= 'mrp.production'   
+    _inherit= 'mrp.production'
 
     def action_confirm(self, cr, uid, ids):
         """ Confirms production order and calculates quantity based on subproduct_type.