diff --git a/bom.py b/bom.py
index 1378dc0b05..737abc47de 100644
--- a/bom.py
+++ b/bom.py
@@ -78,12 +78,9 @@ class BOMInput(ModelSQL, ModelView):
             ('product_bom_uniq', 'UNIQUE(product, bom)',
                 'product_bom_uniq'),
             ]
-        cls._constraints += [
-            ('check_bom_recursion', 'recursive_bom'),
-            ]
         cls._error_messages.update({
-                'product_bom_uniq': 'Product must be unique per BOM!',
-                'recursive_bom': 'You can not create recursive BOMs!',
+                'product_bom_uniq': 'Product must be unique per BOM.',
+                'recursive_bom': 'You can not create recursive BOMs.',
                 })
 
     def on_change_product(self):
@@ -109,11 +106,17 @@ class BOMInput(ModelSQL, ModelView):
             return self.uom.digits
         return 2
 
+    @classmethod
+    def validate(cls, boms):
+        super(BOMInput, cls).validate(boms)
+        for bom in boms:
+            bom.check_bom_recursion()
+
     def check_bom_recursion(self):
         '''
         Check BOM recursion
         '''
-        return self.product.check_bom_recursion()
+        self.product.check_bom_recursion()
 
     def compute_quantity(self, factor):
         Uom = Pool().get('product.uom')
diff --git a/product.py b/product.py
index f9e524d04c..2a1248f63b 100644
--- a/product.py
+++ b/product.py
@@ -21,13 +21,17 @@ class Product:
     @classmethod
     def __setup__(cls):
         super(Product, cls).__setup__()
-        cls._constraints += [
-            ('check_bom_recursion', 'recursive_bom'),
-            ]
         cls._error_messages.update({
-                'recursive_bom': 'You can not create recursive BOMs!',
+                'recursive_bom': ('You are trying to create a recursive BOM '
+                    'with product "%s" which is not allowed.'),
                 })
 
+    @classmethod
+    def validate(cls, products):
+        super(Product, cls).validate(products)
+        for product in products:
+            product.check_bom_recursion()
+
     def check_bom_recursion(self, product=None):
         '''
         Check BOM recursion
@@ -36,11 +40,9 @@ class Product:
             product = self
         for product_bom in self.boms:
             for input_ in product_bom.bom.inputs:
-                if input_.product == product:
-                    return False
-                if not input_.product.check_bom_recursion(product=product):
-                    return False
-        return True
+                if (input_.product == product
+                        or input_.product.check_bom_recursion(product=product)):
+                    self.raise_user_error('recursive_bom', (product.rec_name,))
 
 
 class ProductBom(ModelSQL, ModelView):
diff --git a/production.py b/production.py
index b4e6574f1d..6638001bc7 100644
--- a/production.py
+++ b/production.py
@@ -133,11 +133,9 @@ class Production(Workflow, ModelSQL, ModelView):
     @classmethod
     def __setup__(cls):
         super(Production, cls).__setup__()
-        cls._constraints += [
-            ('check_cost', 'missing_cost'),
-            ]
         cls._error_messages.update({
-                'missing_cost': 'It misses some cost on the outputs!',
+                'missing_cost': ('Production "%s" misses costs on '
+                    'some of its outputs.'),
                 })
         cls._transitions |= set((
                 ('request', 'draft'),
@@ -436,16 +434,21 @@ class Production(Workflow, ModelSQL, ModelView):
                 move.save()
         self._set_move_planned_date()
 
+    @classmethod
+    def validate(cls, productions):
+        super(Production, cls).validate(productions)
+        for production in productions:
+            production.check_cost()
+
     def check_cost(self):
         if self.state != 'done':
-            return True
+            return
         cost_price = Decimal(0)
         for output in self.outputs:
             cost_price += (Decimal(str(output.quantity))
                 * output.unit_price)
         if not self.company.currency.is_zero(self.cost - cost_price):
-            return False
-        return True
+            self.raise_user_error('missing_cost', (self.rec_name,))
 
     @classmethod
     def create(cls, vlist):