diff --git a/libp2p/network/swarm.py b/libp2p/network/swarm.py
index e6bf288..daabb64 100644
--- a/libp2p/network/swarm.py
+++ b/libp2p/network/swarm.py
@@ -5,6 +5,7 @@ from libp2p.protocol_muxer.multiselect import Multiselect
 from libp2p.peer.id import id_b58_decode
 
 from .network_interface import INetwork
+from .notifee_interface import INotifee
 from .stream.net_stream import NetStream
 from .connection.raw_connection import RawConnection
 
@@ -175,8 +176,8 @@ class Swarm(INetwork):
         """
         :param notifee: object implementing Notifee interface
         """
-        # TODO: Add check to ensure notifee conforms to Notifee interface
-        self.notifees.append(notifee)
+        if isinstance(notifee, INotifee):
+            self.notifees.append(notifee)
 
     def add_transport(self, transport):
         # TODO: Support more than one transport
@@ -195,6 +196,10 @@ def create_generic_protocol_handler(swarm):
         # Perform protocol muxing to determine protocol to use
         _, handler = await multiselect.negotiate(muxed_stream)
 
+        # Call notifiers since event occurred
+        for notifee in swarm.notifees:
+            await notifee.opened_stream(swarm, muxed_stream)
+
         # Give to stream handler
         asyncio.ensure_future(handler(muxed_stream))
 
diff --git a/tests/libp2p/test_notify.py b/tests/libp2p/test_notify.py
index fdf7368..37b287a 100644
--- a/tests/libp2p/test_notify.py
+++ b/tests/libp2p/test_notify.py
@@ -44,6 +44,27 @@ class MyNotifee(INotifee):
     async def listen_close(self, network, multiaddr):
         pass
 
+class InvalidNotifee():
+    # pylint: disable=too-many-instance-attributes, cell-var-from-loop
+
+    def __init__(self):
+        pass
+
+    async def opened_stream(self, network, stream):
+        assert False
+
+    async def closed_stream(self, network, stream):
+        assert False
+
+    async def connected(self, network, conn):
+        assert False
+
+    async def disconnected(self, network, conn):
+        assert False
+
+    async def listen(self, network, multiaddr):
+        assert False
+
 async def perform_two_host_simple_set_up():
     node_a = await new_node(transport_opt=["/ip4/127.0.0.1/tcp/0"])
     node_b = await new_node(transport_opt=["/ip4/127.0.0.1/tcp/0"])
@@ -61,6 +82,16 @@ async def perform_two_host_simple_set_up():
     node_a.get_peerstore().add_addrs(node_b.get_id(), node_b.get_addrs(), 10)
     return node_a, node_b
 
+async def perform_two_host_simple_set_up_custom_handler(handler):
+    node_a = await new_node(transport_opt=["/ip4/127.0.0.1/tcp/0"])
+    node_b = await new_node(transport_opt=["/ip4/127.0.0.1/tcp/0"])
+
+    node_b.set_stream_handler("/echo/1.0.0", handler)
+
+    # Associate the peer with local ip address (see default parameters of Libp2p())
+    node_a.get_peerstore().add_addrs(node_b.get_id(), node_b.get_addrs(), 10)
+    return node_a, node_b
+
 @pytest.mark.asyncio
 async def test_one_notifier():
     node_a, node_b = await perform_two_host_simple_set_up()
@@ -88,6 +119,47 @@ async def test_one_notifier():
     # Success, terminate pending tasks.
     await cleanup()
 
+@pytest.mark.asyncio
+async def test_one_notifier_on_two_nodes():
+    events_b = []
+    
+    async def my_stream_handler(stream):
+        assert events_b == [["connectedb", stream.mplex_conn], \
+            ["opened_streamb", stream]]
+        while True:
+            read_string = (await stream.read()).decode()
+
+            resp = "ack:" + read_string
+            await stream.write(resp.encode())
+
+    node_a, node_b = await perform_two_host_simple_set_up_custom_handler(my_stream_handler)
+
+    # Add notifee for node_a
+    events_a = []
+    node_a.get_network().notify(MyNotifee(events_a, "a"))
+
+    # Add notifee for node_b
+    node_b.get_network().notify(MyNotifee(events_b, "b"))
+
+    stream = await node_a.new_stream(node_b.get_id(), ["/echo/1.0.0"])
+
+    # Ensure the connected and opened_stream events were hit in MyNotifee obj
+    # and that stream passed into opened_stream matches the stream created on
+    # node_a
+    assert events_a == [["connecteda", stream.mplex_conn], \
+        ["opened_streama", stream]]
+
+    messages = ["hello", "hello"]
+    for message in messages:
+        await stream.write(message.encode())
+
+        response = (await stream.read()).decode()
+
+        assert response == ("ack:" + message)
+
+    # Success, terminate pending tasks.
+    await cleanup()
+
 @pytest.mark.asyncio
 async def test_two_notifiers():
     node_a, node_b = await perform_two_host_simple_set_up()
@@ -150,3 +222,31 @@ async def test_ten_notifiers():
 
     # Success, terminate pending tasks.
     await cleanup()
+
+@pytest.mark.asyncio
+async def test_invalid_notifee():
+    num_notifiers = 10
+
+    node_a, node_b = await perform_two_host_simple_set_up()
+
+    # Add notifee for node_a
+    events_lst = []
+    for i in range(num_notifiers):
+        events_lst.append([])
+        node_a.get_network().notify(InvalidNotifee())
+
+    stream = await node_a.new_stream(node_b.get_id(), ["/echo/1.0.0"])
+
+    # If this point is reached, this implies that the InvalidNotifee instance
+    # did not assert false, i.e. no functions of InvalidNotifee were called (which is correct
+    # given that InvalidNotifee should not have been added as a notifee)
+    messages = ["hello", "hello"]
+    for message in messages:
+        await stream.write(message.encode())
+
+        response = (await stream.read()).decode()
+
+        assert response == ("ack:" + message)
+
+    # Success, terminate pending tasks.
+    await cleanup()