diff --git a/server/protocol.py b/server/protocol.py
index f7abb20..f75a08a 100644
--- a/server/protocol.py
+++ b/server/protocol.py
@@ -316,33 +316,36 @@ class ServerManager(LoggedClass):
         if self.irc_future:
             self.irc_future.cancel()
         for session in self.sessions:
-            session.transport.close()
+            self.close_session(session)
 
     async def wait_shutdown(self):
         # Wait for servers to close
         for server in self.servers:
             await server.wait_closed()
-        # Just in case a connection came in
-        await asyncio.sleep(0)
         self.servers = []
-        self.logger.info('server listening sockets closed')
-        limit = time.time() + 15
+
+        secs = 60
+        self.logger.info('server listening sockets closed, waiting '
+                         '{:d} seconds for socket cleanup'.format(secs))
+
+        limit = time.time() + secs
         while self.sessions and time.time() < limit:
+            await asyncio.sleep(4)
             self.logger.info('{:,d} sessions remaining'
                              .format(len(self.sessions)))
-            await asyncio.sleep(3)
-        if self.sessions:
-            self.logger.info('forcibly closing {:,d} stragglers'
-                             .format(len(self.sessions)))
-            for future in self.sessions.values():
-                future.cancel()
-            await asyncio.sleep(1)
 
     def add_session(self, session):
-        assert self.servers
-        assert session not in self.sessions
         coro = session.serve_requests()
-        self.sessions[session] = asyncio.ensure_future(coro)
+        future = asyncio.ensure_future(coro)
+        self.sessions[session] = future
+        # Some connections are acknowledged after the servers are closed
+        if not self.servers:
+            self.close_session(session)
+
+    def close_session(self, session):
+        '''Close the session's transport and cancel its future.'''
+        session.transport.close()
+        self.sessions[session].cancel()
 
     def remove_session(self, session):
         self.subscription_count -= session.sub_count()