diff --git a/minode/connection.py b/minode/connection.py
index 05d552a..3a449ac 100644
--- a/minode/connection.py
+++ b/minode/connection.py
@@ -380,10 +380,16 @@ class ConnectionBase(threading.Thread):
         if (
             version.protocol_version != shared.protocol_version
             or version.nonce == shared.nonce
+            or version.nonce in shared.nonce_pool.values()
         ):
+            logging.warning(
+                'Disconnecting v%s node %s with nonce %s',
+                version.protocol_version, self.host_print,
+                base64.b16encode(version.nonce))
             self.status = 'disconnecting'
             self.send_queue.put(None)
         else:
+            shared.nonce_pool[self.host] = version.nonce
             logging.info(
                 '%s:%s claims to be %s',
                 self.host_print, self.port, version.user_agent)
diff --git a/minode/manager.py b/minode/manager.py
index 71f5873..fa9acad 100644
--- a/minode/manager.py
+++ b/minode/manager.py
@@ -106,6 +106,10 @@ class Manager(threading.Thread):
             if not c.is_alive() or c.status == 'disconnected':
                 with shared.connections_lock:
                     shared.connections.remove(c)
+                try:
+                    del shared.nonce_pool[c.host]
+                except KeyError:
+                    pass
             else:
                 hosts.add(structure.NetAddrNoPrefix.network_group(c.host))
                 if not c.server:
diff --git a/minode/shared.py b/minode/shared.py
index 72864ec..d5ac8f4 100644
--- a/minode/shared.py
+++ b/minode/shared.py
@@ -54,6 +54,7 @@ core_nodes = set()
 
 node_pool = set()
 unchecked_node_pool = set()
+nonce_pool = {}
 
 i2p_core_nodes = set()
 i2p_node_pool = set()