diff --git a/lodel/leapi/leobject.py b/lodel/leapi/leobject.py
index 93bf435..871914c 100644
--- a/lodel/leapi/leobject.py
+++ b/lodel/leapi/leobject.py
@@ -265,8 +265,8 @@ class LeObject(object):
         expt_msg = "In LeAPI class '%s' " % cls.__name__
         if ds_name not in Settings.datasources._fields:
             #Checking that datasource exists
-            expt_msg += "Unknow or unconfigured datasource %s"
-            expt_msg %= (ds_name, cls.__name__)
+            expt_msg += "Unknown or unconfigured datasource %s"
+            expt_msg %= (ds_name) # , cls.__name__)
             raise SettingsError(expt_msg)
         try:
             #fetching plugin name
diff --git a/plugins/mongodb_datasource/datasource.py b/plugins/mongodb_datasource/datasource.py
index aa295b1..6383384 100644
--- a/plugins/mongodb_datasource/datasource.py
+++ b/plugins/mongodb_datasource/datasource.py
@@ -93,7 +93,7 @@ class MongoDbDatasource(object):
     def select(self, target, field_list, filters = None, rel_filters=None, order=None, group=None, limit=None,
                offset=0):
         results = list()
-        if target.abstract:
+        if hasattr(target, '_abstract') and target._abstract:
             target_childs = target.child_classes()
             for target_child in target_childs:
                 results.append(self.select(target=target_child, field_list=field_list, filters=filters,