diff --git a/klippy/extras/motion_queuing.py b/klippy/extras/motion_queuing.py
index 91060019..55a7b929 100644
--- a/klippy/extras/motion_queuing.py
+++ b/klippy/extras/motion_queuing.py
@@ -13,6 +13,7 @@ class PrinterMotionQueuing:
         self.trapqs = []
         self.stepcompress = []
         self.steppersyncs = []
+        self.flush_callbacks = []
         ffi_main, ffi_lib = chelper.get_ffi()
         self.trapq_finalize_moves = ffi_lib.trapq_finalize_moves
     def allocate_trapq(self):
@@ -40,7 +41,11 @@ class PrinterMotionQueuing:
         return ss
     def register_stepper(self, config, stepper):
         self.steppers.append(stepper)
+    def register_flush_callback(self, callback):
+        self.flush_callbacks.append(callback)
     def flush_motion_queues(self, must_flush_time, max_step_gen_time):
+        for cb in self.flush_callbacks:
+            cb(must_flush_time)
         for stepper in self.steppers:
             stepper.generate_steps(max_step_gen_time)
     def clean_motion_queues(self, trapq_free_time, clear_history_time):
diff --git a/klippy/extras/output_pin.py b/klippy/extras/output_pin.py
index 05266382..9eb8ea8b 100644
--- a/klippy/extras/output_pin.py
+++ b/klippy/extras/output_pin.py
@@ -20,11 +20,12 @@ class GCodeRequestQueue:
         self.rqueue = []
         self.next_min_flush_time = 0.
         self.toolhead = None
-        mcu.register_flush_callback(self._flush_notification)
+        motion_queuing = printer.load_object(config, 'motion_queuing')
+        motion_queuing.register_flush_callback(self._flush_notification)
         printer.register_event_handler("klippy:connect", self._handle_connect)
     def _handle_connect(self):
         self.toolhead = self.printer.lookup_object('toolhead')
-    def _flush_notification(self, print_time, clock):
+    def _flush_notification(self, print_time):
         min_sched_time = self.mcu.min_schedule_time()
         rqueue = self.rqueue
         while rqueue:
diff --git a/klippy/extras/pwm_tool.py b/klippy/extras/pwm_tool.py
index a0739b5b..69fc1a46 100644
--- a/klippy/extras/pwm_tool.py
+++ b/klippy/extras/pwm_tool.py
@@ -46,12 +46,13 @@ class MCU_queued_pwm:
         self._start_value = max(0., min(1., start_value))
         self._shutdown_value = max(0., min(1., shutdown_value))
     def _build_config(self):
-        config_error = self._mcu.get_printer().config_error
+        printer = self._mcu.get_printer()
+        config_error = printer.config_error
         if self._max_duration and self._start_value != self._shutdown_value:
             raise config_error("Pin with max duration must have start"
                                " value equal to shutdown value")
         cmd_queue = self._mcu.alloc_command_queue()
-        curtime = self._mcu.get_printer().get_reactor().monotonic()
+        curtime = printer.get_reactor().monotonic()
         printtime = self._mcu.estimated_print_time(curtime)
         self._last_clock = self._mcu.print_time_to_clock(printtime + 0.200)
         cycle_ticks = self._mcu.seconds_to_clock(self._cycle_time)
@@ -61,7 +62,8 @@ class MCU_queued_pwm:
         if self._duration_ticks >= 1<<31:
             raise config_error("PWM pin max duration too large")
         if self._duration_ticks:
-            self._mcu.register_flush_callback(self._flush_notification)
+            motion_queuing = printer.lookup_object('motion_queuing')
+            motion_queuing.register_flush_callback(self._flush_notification)
         if self._hardware_pwm:
             self._pwm_max = self._mcu.get_constant_float("PWM_MAX")
             self._default_value = self._shutdown_value * self._pwm_max
@@ -122,7 +124,8 @@ class MCU_queued_pwm:
             value = 1. - value
         v = int(max(0., min(1., value)) * self._pwm_max + 0.5)
         self._send_update(clock, v)
-    def _flush_notification(self, print_time, clock):
+    def _flush_notification(self, print_time):
+        clock = self._mcu.print_time_to_clock(print_time)
         if self._last_value != self._default_value:
             while clock >= self._last_clock + self._duration_ticks:
                 self._send_update(self._last_clock + self._duration_ticks,
diff --git a/klippy/mcu.py b/klippy/mcu.py
index d7665036..c8bc9c9b 100644
--- a/klippy/mcu.py
+++ b/klippy/mcu.py
@@ -606,7 +606,6 @@ class MCU:
                                                   minval=0.)
         self._reserved_move_slots = 0
         self._steppersync = None
-        self._flush_callbacks = []
         # Stats
         self._get_status_info = {}
         self._stats_sumsq_base = 0.
@@ -971,16 +970,12 @@ class MCU:
     # Move queue tracking
     def request_move_queue_slot(self):
         self._reserved_move_slots += 1
-    def register_flush_callback(self, callback):
-        self._flush_callbacks.append(callback)
     def flush_moves(self, print_time, clear_history_time):
         if self._steppersync is None:
             return
         clock = self.print_time_to_clock(print_time)
         if clock < 0:
             return
-        for cb in self._flush_callbacks:
-            cb(print_time, clock)
         clear_history_clock = \
             max(0, self.print_time_to_clock(clear_history_time))
         ret = self._ffi_lib.steppersync_flush(self._steppersync, clock,