diff --git a/product/ERP5/Document/TransactionQuantityValueValidityConstraint.py b/product/ERP5/Document/TransactionQuantityValueValidityConstraint.py
new file mode 100644
index 0000000000000000000000000000000000000000..d77987a8a8cbcf8ab95254be534a50f1e680af19
--- /dev/null
+++ b/product/ERP5/Document/TransactionQuantityValueValidityConstraint.py
@@ -0,0 +1,79 @@
+##############################################################################
+#
+# Copyright (c) 2006 Nexedi SARL and Contributors. All Rights Reserved.
+#             Romain Courteaud <romain@nexedi.com>
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsability of assessing all potential
+# consequences resulting from its eventual inadequacies and bugs
+# End users who are looking for a ready-to-use solution with commercial
+# garantees and support are strongly adviced to contract a Free Software
+# Service Company
+#
+# This program is Free Software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+#
+##############################################################################
+
+from Products.ERP5Type.mixin.constraint import ConstraintMixin
+from Products.ERP5Type import PropertySheet
+
+class TransactionQuantityValueValidityConstraint(ConstraintMixin):
+    """
+    This is only relevant for ZODB Property Sheets (filesystem Property
+    Sheets rely on Products.ERP5.Constraint.TransactionQuantityValueValidity
+    instead).
+    """
+    meta_type = 'ERP5 Transaction Quantity Value Validity Constraint'
+    portal_type = 'Transaction Quantity Value Validity Constraint'
+
+    property_sheets = (PropertySheet.SimpleItem,
+                       PropertySheet.Predicate,
+                       PropertySheet.Reference)
+
+    def checkConsistency(self, object, fixit=0):
+      """
+      Check if the quantity of the transaction is greater than the
+      balance of the source.
+      """
+      if not self.test(object):
+          return []
+
+      errors = []
+
+      source_cell = object.getSourceValue()
+      destination_cell = object.getDestinationValue()
+
+      if (source_cell is not None) and \
+         (destination_cell is not None):
+        # XXX Dirty code !
+        quantity = object.getQuantity()
+        budget_list = object.getPortalObject().budget_module.objectValues()
+        max_quantity = 0
+        for obj in budget_list:
+          for item in obj.objectValues():
+             if (item.getPortalType() == 'Budget Transfer Line') and \
+                (item.getSourceValue() == source_cell) and \
+                (item.getDestinationValue() == destination_cell):
+               max_quantity = item.getQuantity()
+        if quantity > max_quantity:
+          if fixit != 0:
+            self.setQuantity(max_quantity)
+          else:
+            error_message = 'The quantity of the transaction is greater than ' \
+                            'the transferable maximum quantity (TMQ): ' \
+                            'TMQ = %.2f' % max_quantity
+            # Add error
+            errors.append(self._generateError(object, error_message))
+      return errors