diff --git a/pyroute2/ndb/source.py b/pyroute2/ndb/source.py
index e068322d2..a8c4a2c15 100644
--- a/pyroute2/ndb/source.py
+++ b/pyroute2/ndb/source.py
@@ -7,10 +7,21 @@
 starts with one local RTNL source names `localhost`::
 
     >>> ndb = NDB()
-    >>> ndb.sources.details()
-    {'kind': u'local', u'nlm_generator': 1, 'target': u'localhost'}
+    >>> ndb.sources.summary().format("json")
+    [
+        {
+            "name": "localhost",
+            "spec": "{'target': 'localhost', 'nlm_generator': 1}",
+            "state": "running"
+        },
+        {
+            "name": "localhost/nsmanager",
+            "spec": "{'target': 'localhost/nsmanager'}",
+            "state": "running"
+        }
+    ]
     >>> ndb.sources['localhost']
-    [running] <IPRoute {'nlm_generator': 1}>
+    [running] <IPRoute {'target: 'localhost', 'nlm_generator': 1}>
 
 The `localhost` RTNL source starts an additional async cache thread.
 The `nlm_generator` option means that instead of collections the
@@ -18,7 +29,7 @@
 consume memory regardless of the RTNL objects number::
 
     >>> ndb.sources['localhost'].nl.link('dump')
-    <generator object _match at 0x7fa444961e10>
+    <generator object RTNL_API.filter_messages at 0x7f61a99a34a0>
 
 See also: :ref:`iproute`
 
@@ -180,6 +191,12 @@ def __init__(self, ndb, **spec):
         self.ndb.task_manager.db_add_nl_source(self.target, self.kind, spec)
         self.load_sql()
 
+    @classmethod
+    def _count(cls, view):
+        return view.ndb.task_manager.db_fetchone(
+            "SELECT count(*) FROM %s" % view.table
+        )
+
     @property
     def must_restart(self):
         if self.max_errors < 0 or self.errors_counter <= self.max_errors:
diff --git a/tests/test_linux/test_ndb/test_sources.py b/tests/test_linux/test_ndb/test_sources.py
index c53be96af..25177df97 100644
--- a/tests/test_linux/test_ndb/test_sources.py
+++ b/tests/test_linux/test_ndb/test_sources.py
@@ -38,6 +38,7 @@ def test_multiple_sources(context):
         assert len(list(ndb.neighbours.dump()))
         assert len(list(ndb.addresses.dump()))
         assert len(list(ndb.routes.dump()))
+        assert len(ndb.sources) == len(sources)
     # here NDB() gets closed
     #