diff --git a/account_constraints/account_constraints.py b/account_constraints/account_constraints.py
index 8190e9854..419ffcb95 100644
--- a/account_constraints/account_constraints.py
+++ b/account_constraints/account_constraints.py
@@ -44,9 +44,22 @@ class AccountMove(orm.Model):
 class AccountMoveLine(orm.Model):
     _inherit = 'account.move.line'
 
-    def _check_invoice_related_move(self, cr, uid, ids, context=None):
+    def _authorized_reconcile(self, vals):
+        """ Check if only reconcile_id and/or reconcile_partial_id are altered. We
+        cannot change other vals, but we should be able to write or unlink those field
+        (e.g. when you want to manually unreconcile an entry generated by an invoice).
+        """
+        if not vals:
+            return False
+        rec_keys = set(["reconcile_id", "reconcile_partial_id"])
+        write_keys = set(vals)
+        return rec_keys.issuperset(write_keys)
+
+    def _check_invoice_related_move(self, cr, uid, ids, vals=None, context=None):
         for line in self.browse(cr, uid, ids, context=context):
             if line.invoice:
+                if self._authorized_reconcile(vals):
+                    return True
                 err_msg = (_('Invoice name (id): %s (%s)') %
                             (line.invoice.name, line.invoice.id))
                 raise osv.except_osv(
@@ -55,9 +68,11 @@ class AccountMoveLine(orm.Model):
                     'change the related invoice directly.\n%s.') % err_msg)
         return True
 
-    def _check_statement_related_move(self, cr, uid, ids, context=None):
+    def _check_statement_related_move(self, cr, uid, ids, vals=None, context=None):
         for line in self.browse(cr, uid, ids, context=context):
             if line.statement_id:
+                if self._authorized_reconcile(vals):
+                    return True
                 err_msg = (_('Bank statement name (id): %s (%s)') %
                             (line.statement_id.name, line.statement_id.id))
                 raise osv.except_osv(
@@ -71,6 +86,7 @@ class AccountMoveLine(orm.Model):
 
         - Is the move related to an invoice
         - Is the move related to a bank statement
+        - Is other values than reconcile_partial_id and/or reconcile_id modified
 
         In that case, we forbid the move to be deleted even if draft. We
         should never delete directly a move line related or generated by
@@ -89,6 +105,7 @@ class AccountMoveLine(orm.Model):
 
         - Is the move related to an invoice
         - Is the move related to a bank statement
+        - Is other values than reconcile_partial_id and/or reconcile_id modified
 
         In that case, we forbid the move to be modified even if draft.
         We should never update directly a move line related or generated
@@ -98,8 +115,8 @@ class AccountMoveLine(orm.Model):
         if context is None:
             context = {}
         if not context.get('from_parent_object', False):
-            self._check_invoice_related_move(cr, uid, ids, context=context)
-            self._check_statement_related_move(cr, uid, ids, context=context)
+            self._check_invoice_related_move(cr, uid, ids, vals, context=context)
+            self._check_statement_related_move(cr, uid, ids, vals, context=context)
         return super(AccountMoveLine, self).write(cr, uid, ids, vals,
             context=context, check=check, update_check=update_check)