diff --git a/klippy/homing.py b/klippy/homing.py
index 4d5ab505..384da3dd 100644
--- a/klippy/homing.py
+++ b/klippy/homing.py
@@ -78,7 +78,7 @@ class Homing:
             try:
                 if es.check_busy(self.eventtime):
                     return True
-            except mcu.MCUError, e:
+            except mcu.error, e:
                 raise EndstopError("Failed to home stepper %s: %s" % (
                     stepper.name, str(e)))
             post_home_pos = stepper.mcu_stepper.get_mcu_position()
@@ -110,7 +110,7 @@ class QueryEndstops:
             try:
                 if self.busy[0][1].check_busy(eventtime):
                     return True
-            except mcu.MCUError, e:
+            except mcu.error, e:
                 raise EndstopError("Failed to query endstop %s: %s" % (
                     self.busy[0][0], str(e)))
             self.busy.pop(0)
@@ -125,10 +125,7 @@ class QueryEndstops:
         return False
 
 class EndstopError(Exception):
-    def __init__(self, msg="Endstop error"):
-        self._msg = msg
-    def __str__(self):
-        return self._msg
+    pass
 
 def EndstopMoveError(pos, msg="Move out of range"):
     return EndstopError("%s: %.3f %.3f %.3f [%.3f]" % (
diff --git a/klippy/mcu.py b/klippy/mcu.py
index 200c6256..1c309f6c 100644
--- a/klippy/mcu.py
+++ b/klippy/mcu.py
@@ -6,11 +6,8 @@
 import sys, zlib, logging, time, math
 import serialhdl, pins, chelper
 
-class MCUError(Exception):
-    def __init__(self, msg="MCU Error"):
-        self._msg = msg
-    def __str__(self):
-        return self._msg
+class error(Exception):
+    pass
 
 def parse_pin_extras(pin, can_pullup=False):
     pullup = invert = 0
@@ -167,9 +164,9 @@ class MCU_endstop:
                 # Timeout - disable endstop checking
                 msg = self._home_cmd.encode(self._oid, 0, 0, 0)
                 self._mcu.send(msg, reqclock=0, cq=self._cmd_queue)
-                raise MCUError("Timeout during endstop homing")
+                raise error("Timeout during endstop homing")
         if self._mcu.is_shutdown:
-            raise MCUError("MCU is shutdown")
+            raise error("MCU is shutdown")
         last_clock = self._mcu.get_last_clock()
         if last_clock >= self._next_query_clock:
             self._next_query_clock = last_clock + self._retry_query_ticks
diff --git a/klippy/msgproto.py b/klippy/msgproto.py
index 73c8d2d5..76dc0544 100644
--- a/klippy/msgproto.py
+++ b/klippy/msgproto.py
@@ -24,10 +24,7 @@ MESSAGE_DEST = 0x10
 MESSAGE_SYNC = '\x7E'
 
 class error(Exception):
-    def __init__(self, msg):
-        self.msg = msg
-    def __str__(self):
-        return self.msg
+    pass
 
 def crc16_ccitt(buf):
     crc = 0xffff