diff --git a/pyModeS/extra/rtlreader.py b/pyModeS/extra/rtlreader.py
index 3c40ebc..d14f270 100644
--- a/pyModeS/extra/rtlreader.py
+++ b/pyModeS/extra/rtlreader.py
@@ -31,6 +31,8 @@ class RtlReader(object):
         self.stop_flag = False
         self.noise_floor = 1e6
 
+        self.exception_queue = None
+
     def _calc_noise(self):
         """Calculate noise floor"""
         window = smaples_per_microsec * 100
@@ -162,6 +164,7 @@ class RtlReader(object):
 
     def run(self, raw_pipe_in=None, stop_flag=None, exception_queue=None):
         self.raw_pipe_in = raw_pipe_in
+        self.exception_queue = exception_queue
         self.stop_flag = stop_flag
 
         try:
@@ -173,8 +176,8 @@ class RtlReader(object):
 
         except Exception as e:
             tb = traceback.format_exc()
-            if exception_queue is not None:
-                exception_queue.put(tb)
+            if self.exception_queue is not None:
+                self.exception_queue.put(tb)
             raise e
 
 
diff --git a/pyModeS/extra/tcpclient.py b/pyModeS/extra/tcpclient.py
index 26be3be..b9e1ca4 100644
--- a/pyModeS/extra/tcpclient.py
+++ b/pyModeS/extra/tcpclient.py
@@ -28,6 +28,8 @@ class TcpClient(object):
         self.raw_pipe_in = None
         self.stop_flag = False
 
+        self.exception_queue = None
+
     def connect(self):
         self.socket = zmq.Context().socket(zmq.STREAM)
         self.socket.setsockopt(zmq.LINGER, 0)
@@ -255,6 +257,7 @@ class TcpClient(object):
 
     def run(self, raw_pipe_in=None, stop_flag=None, exception_queue=None):
         self.raw_pipe_in = raw_pipe_in
+        self.exception_queue = exception_queue
         self.stop_flag = stop_flag
         self.connect()
 
@@ -286,7 +289,8 @@ class TcpClient(object):
                 continue
             except Exception as e:
                 tb = traceback.format_exc()
-                exception_queue.put(tb)
+                if self.exception_queue is not None:
+                    self.exception_queue.put(tb)
                 raise e