diff --git a/addons/mrp_byproduct/mrp_byproduct.py b/addons/mrp_byproduct/mrp_byproduct.py
index 91ea997a2e44db28ce16d48e4f8d37712e8ff5b3..fc6069fc8ad9011e3fc5be6f8b1e5b685b9b7a0b 100644
--- a/addons/mrp_byproduct/mrp_byproduct.py
+++ b/addons/mrp_byproduct/mrp_byproduct.py
@@ -35,7 +35,7 @@ class mrp_subproduct(osv.osv):
   'Fixed' depicts a situation where the quantity of created byproduct is always equal to the quantity set on the BoM, regardless of how many are created in the production order.\
   By opposition, 'Variable' means that the quantity will be computed as\
     '(quantity of byproduct set on the BoM / quantity of manufactured product set on the BoM * quantity of manufactured product in the production order.)'"),
-        'bom_id': fields.many2one('mrp.bom', 'BoM'),
+        'bom_id': fields.many2one('mrp.bom', 'BoM', ondelete='cascade'),
     }
     _defaults={
         'subproduct_type': 'variable',