diff --git a/klippy/mcu.py b/klippy/mcu.py
index 751e55ef..4fa7772b 100644
--- a/klippy/mcu.py
+++ b/klippy/mcu.py
@@ -254,6 +254,9 @@ class MCU_digital_out:
             self._mcu.add_config_cmd("set_digital_out pin=%s value=%d"
                                      % (self._pin, self._start_value))
             return
+        if self._max_duration and self._start_value != self._shutdown_value:
+            raise pins.error("Pin with max duration must have start"
+                             " value equal to shutdown value")
         self._mcu.request_move_queue_slot()
         self._oid = self._mcu.create_oid()
         self._mcu.add_config_cmd(
@@ -305,6 +308,9 @@ class MCU_pwm:
         self._shutdown_value = max(0., min(1., shutdown_value))
         self._is_static = is_static
     def _build_config(self):
+        if self._max_duration and self._start_value != self._shutdown_value:
+            raise pins.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()
         printtime = self._mcu.estimated_print_time(curtime)