diff --git a/addons/mrp/models/mrp_unbuild.py b/addons/mrp/models/mrp_unbuild.py
index 328a51123a7..696f605c220 100644
--- a/addons/mrp/models/mrp_unbuild.py
+++ b/addons/mrp/models/mrp_unbuild.py
@@ -116,7 +116,7 @@ class MrpUnbuild(models.Model):
     def _onchange_product_id(self):
         if self.product_id:
             self.bom_id = self.env['mrp.bom']._bom_find(self.product_id, company_id=self.company_id.id)[self.product_id]
-            self.product_uom_id = self.product_id.uom_id.id
+            self.product_uom_id = self.mo_id.product_id == self.product_id and self.mo_id.product_uom_id.id or self.product_id.uom_id.id
 
     @api.constrains('product_qty')
     def _check_qty(self):