diff --git a/klippy/mcu.py b/klippy/mcu.py
index 507f77347..20ffc3fdf 100644
--- a/klippy/mcu.py
+++ b/klippy/mcu.py
@@ -60,14 +60,14 @@ class RetryAsyncCommand:
 
 # Wrapper around query commands
 class CommandQueryWrapper:
-    def __init__(self, serial, msgformat, respformat, oid=None,
-                 cmd_queue=None, is_async=False, error=serialhdl.error):
-        self._serial = serial
+    def __init__(self, conn_helper, msgformat, respformat, oid=None,
+                 cmd_queue=None, is_async=False):
+        self._serial = serial = conn_helper.get_serial()
         self._cmd = serial.get_msgparser().lookup_command(msgformat)
         serial.get_msgparser().lookup_command(respformat)
         self._response = respformat.split()[0]
         self._oid = oid
-        self._error = error
+        self._error = conn_helper.get_mcu().get_printer().command_error
         self._xmit_helper = serialhdl.SerialRetryCommand
         if is_async:
             self._xmit_helper = RetryAsyncCommand
@@ -92,15 +92,15 @@ class CommandQueryWrapper:
 
 # Wrapper around command sending
 class CommandWrapper:
-    def __init__(self, serial, msgformat, cmd_queue=None, debugoutput=False):
-        self._serial = serial
+    def __init__(self, conn_helper, msgformat, cmd_queue=None):
+        self._serial = serial = conn_helper.get_serial()
         msgparser = serial.get_msgparser()
         self._cmd = msgparser.lookup_command(msgformat)
         if cmd_queue is None:
             cmd_queue = serial.get_default_command_queue()
         self._cmd_queue = cmd_queue
         self._msgtag = msgparser.lookup_msgid(msgformat) & 0xffffffff
-        if debugoutput:
+        if conn_helper.get_mcu().is_fileoutput():
             # Can't use send_wait_ack when in debugging mode
             self.send_wait_ack = self.send
     def send(self, data=(), minclock=0, reqclock=0):
@@ -1096,12 +1096,11 @@ class MCU:
     def max_nominal_duration(self):
         return MAX_NOMINAL_DURATION
     def lookup_command(self, msgformat, cq=None):
-        return CommandWrapper(self._serial, msgformat, cq,
-                              debugoutput=self.is_fileoutput())
+        return CommandWrapper(self._conn_helper, msgformat, cq)
     def lookup_query_command(self, msgformat, respformat, oid=None,
                              cq=None, is_async=False):
-        return CommandQueryWrapper(self._serial, msgformat, respformat, oid,
-                                   cq, is_async, self._printer.command_error)
+        return CommandQueryWrapper(self._conn_helper, msgformat, respformat,
+                                   oid, cq, is_async)
     def try_lookup_command(self, msgformat):
         try:
             return self.lookup_command(msgformat)