diff --git a/lib/rest.py b/lib/rest.py
index 0a75600..ab9a8f9 100644
--- a/lib/rest.py
+++ b/lib/rest.py
@@ -22,7 +22,7 @@
 from sqlalchemy.orm.exc import NoResultFound
 from pyramid.httpexceptions import HTTPNotFound, HTTPBadRequest, HTTPServerError
 from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session, scoped_session
+from sqlalchemy.orm import sessionmaker, Session, scoped_session, class_mapper
 from pyramid.config import Configurator
 from pyramid.request import Request
 
@@ -595,7 +595,7 @@ def description(self, request):
         """
         return self.model.description(self.dictionary)
 
-    def m_to_n_handling(self, key, value):
+    def m_to_n_handling(self, key, value, session):
         """
         Small helper method. It checks if the passed key is defined as an m_to_n relation ship to other tables. If
         it is: The method gets the corresponding objects from database by the passed (comma seperated) id's and return
@@ -605,6 +605,8 @@ def m_to_n_handling(self, key, value):
         :type key: str
         :param value: The effective value which is intended to be set to the column
         :type value:
+        :param session: The session instance which should be used by this method
+        :type session: Session
         :return: The found results of corresponding datasets or False if the checked column was not a m_to_n one
         :rtype: bool or list
         """
@@ -612,12 +614,12 @@ def m_to_n_handling(self, key, value):
             # found the column which is m:n
             if column.get('is_m_to_n') and key == column.get('column_name'):
                 value_list = str(value).split(',')
-                bound_model = getattr(self.model, key).argument
+                bound_model = class_mapper(self.model).get_property(key).argument
                 pk_name = bound_model.description(self.dictionary).get('pk_name')
                 pk_column = getattr(bound_model, pk_name)
                 relation_list = []
                 for identifier in value_list:
-                    result = self.session.query(bound_model).filter(pk_column == identifier).one()
+                    result = session.query(bound_model).filter(pk_column == identifier).one()
                     relation_list.append(result)
                 return relation_list
         return False
@@ -645,7 +647,7 @@ def create(self, request):
                     m_to_n = self.m_to_n_handling(key, value)
                     if m_to_n:
                         value = m_to_n
-                    setattr(new_record, key, value)
+                    setattr(new_record, key, value, session)
                 session.add(new_record)
                 session.flush()
                 request.response.status_int = 201
@@ -683,7 +685,7 @@ def update(self, request):
                 for key, value in data.iteritems():
                     if key == 'geom':
                         value = WKBSpatialElement(buffer(wkt.loads(value).wkb), srid=2056)
-                    m_to_n = self.m_to_n_handling(key, value)
+                    m_to_n = self.m_to_n_handling(key, value, session)
                     if m_to_n:
                         value = m_to_n
                     setattr(element, key, value)