diff --git a/addons/account/invoice.py b/addons/account/invoice.py
index 6c5db1cb61a..6f39652d34b 100644
--- a/addons/account/invoice.py
+++ b/addons/account/invoice.py
@@ -1451,11 +1451,21 @@ class account_invoice_line(osv.osv):
         return res_final
 
     def uos_id_change(self, cr, uid, ids, product, uom, qty=0, name='', type='out_invoice', partner_id=False, fposition_id=False, price_unit=False, address_invoice_id=False, currency_id=False, context=None):
-        res = self.product_id_change(cr, uid, ids, product, uom, qty, name, type, partner_id, fposition_id, price_unit, address_invoice_id, currency_id, context)
+        warning = {}
+        res = self.product_id_change(cr, uid, ids, product, uom, qty, name, type, partner_id, fposition_id, price_unit, address_invoice_id, currency_id, context=context)
         if 'uos_id' in res['value']:
             del res['value']['uos_id']
         if not uom:
             res['value']['price_unit'] = 0.0
+        if product and uom:
+            prod = self.pool.get('product.product').browse(cr, uid, product, context=context)
+            prod_uom = self.pool.get('product.uom').browse(cr, uid, uom, context=context)
+            if prod.uom_id.category_id.id != prod_uom.category_id.id:
+                 warning = {
+                    'title': _('Warning!'),
+                    'message': _('You selected an Unit of Measure which is not compatible with the product.')
+            }
+            return {'value': res['value'], 'warning': warning}
         return res
 
     def move_line_get(self, cr, uid, invoice_id, context=None):