diff --git a/ipykernel/control.py b/ipykernel/control.py
index 57a7ac727..7ac56b7f9 100644
--- a/ipykernel/control.py
+++ b/ipykernel/control.py
@@ -9,7 +9,7 @@
 
 class ControlThread(Thread):
 
-    def __init__(self, log=None, **kwargs):
+    def __init__(self, **kwargs):
         Thread.__init__(self, **kwargs)
         self.io_loop = IOLoop(make_current=False)
         self.pydev_do_not_trace = True
diff --git a/ipykernel/kernelapp.py b/ipykernel/kernelapp.py
index 090e62e05..7bf4a54ba 100644
--- a/ipykernel/kernelapp.py
+++ b/ipykernel/kernelapp.py
@@ -301,7 +301,8 @@ def init_control(self, context):
 
         self.debug_shell_socket = context.socket(zmq.DEALER)
         self.debug_shell_socket.linger = 1000
-        self.debug_shell_socket.connect(self.shell_socket.getsockopt(zmq.LAST_ENDPOINT))
+        if self.shell_socket.getsockopt(zmq.LAST_ENDPOINT):
+            self.debug_shell_socket.connect(self.shell_socket.getsockopt(zmq.LAST_ENDPOINT))
 
         if hasattr(zmq, 'ROUTER_HANDOVER'):
             # set router-handover to workaround zeromq reconnect problems
@@ -345,7 +346,10 @@ def close(self):
             self.iopub_thread.stop()
             self.iopub_thread.close()
 
-        self.debug_shell_socket.close()
+        if self.debugpy_socket and not self.debugpy_socket.closed:
+            self.debugpy_socket.close()
+        if self.debug_shell_socket and not self.debug_shell_socket.closed:
+            self.debug_shell_socket.close()
 
         for channel in ('shell', 'control', 'stdin'):
             self.log.debug("Closing %s channel", channel)
diff --git a/ipykernel/kernelbase.py b/ipykernel/kernelbase.py
index 0643fcd7b..7b2917d23 100644
--- a/ipykernel/kernelbase.py
+++ b/ipykernel/kernelbase.py
@@ -187,8 +187,8 @@ def __init__(self, **kwargs):
                                  self.session)
 
         self.control_queue = Queue()
-        kwargs['control_thread'].io_loop.add_callback(self.poll_control_queue)
-
+        if 'control_thread' in kwargs:
+            kwargs['control_thread'].io_loop.add_callback(self.poll_control_queue)
 
     @gen.coroutine
     def dispatch_debugpy(self, msg):