diff --git a/klippy/console.py b/klippy/console.py
index c862ba9e..cd7facfd 100755
--- a/klippy/console.py
+++ b/klippy/console.py
@@ -55,8 +55,8 @@ class KeyboardReader:
         self.clocksync.connect(self.ser)
         self.ser.handle_default = self.handle_default
         self.mcu_freq = self.ser.msgparser.get_constant_float('CLOCK_FREQ')
-        mcu = self.ser.msgparser.get_constant('MCU')
-        self.pins = pins.get_pin_map(mcu)
+        mcu_type = self.ser.msgparser.get_constant('MCU')
+        self.pins = pins.PinResolver(mcu_type, validate_aliases=False)
         self.reactor.unregister_timer(self.connect_timer)
         self.output("="*20 + "       connected       " + "="*20)
         return self.reactor.NEVER
@@ -71,8 +71,7 @@ class KeyboardReader:
         self.eval_globals['freq'] = self.mcu_freq
         self.eval_globals['clock'] = self.clocksync.get_clock(eventtime)
     def command_PINS(self, parts):
-        mcu = self.ser.msgparser.get_constant('MCU')
-        self.pins = pins.get_pin_map(mcu, parts[1])
+        self.pins.update_aliases(parts[1])
     def command_SET(self, parts):
         val = parts[2]
         try:
@@ -156,7 +155,7 @@ class KeyboardReader:
             self.output("Eval: %s" % (line,))
         if self.pins is not None:
             try:
-                line = pins.update_command(line, self.pins).strip()
+                line = self.pins.update_command(line).strip()
             except:
                 self.output("Unable to map pin: %s" % (line,))
                 return None
diff --git a/klippy/mcu.py b/klippy/mcu.py
index b5631f4e..a415ba25 100644
--- a/klippy/mcu.py
+++ b/klippy/mcu.py
@@ -522,15 +522,14 @@ class MCU:
             self._oid_count,))
 
         # Resolve pin names
-        mcu = self._serial.msgparser.get_constant('MCU')
-        pnames = pins.get_pin_map(mcu, self._pin_map)
-        updated_cmds = []
-        for cmd in self._config_cmds:
-            try:
-                updated_cmds.append(pins.update_command(cmd, pnames))
-            except:
-                raise pins.error("Unable to translate pin name: %s" % (cmd,))
-        self._config_cmds = updated_cmds
+        mcu_type = self._serial.msgparser.get_constant('MCU')
+        pin_resolver = pins.PinResolver(mcu_type)
+        if self._pin_map is not None:
+            pin_resolver.update_aliases(self._pin_map)
+        for i, cmd in enumerate(self._config_cmds):
+            self._config_cmds[i] = pin_resolver.update_command(cmd)
+        for i, cmd in enumerate(self._init_cmds):
+            self._init_cmds[i] = pin_resolver.update_command(cmd)
 
         # Calculate config CRC
         self._config_crc = zlib.crc32('\n'.join(self._config_cmds)) & 0xffffffff
diff --git a/klippy/pins.py b/klippy/pins.py
index c612432c..c7983280 100644
--- a/klippy/pins.py
+++ b/klippy/pins.py
@@ -152,21 +152,32 @@ def update_map_beaglebone(pins, mcu):
 # Command translation
 ######################################################################
 
-# Obtains the pin mappings
-def get_pin_map(mcu, mapping_name=None):
-    pins = dict(MCU_PINS.get(mcu, {}))
-    if mapping_name == 'arduino':
-        update_map_arduino(pins, mcu)
-    elif mapping_name == 'beaglebone':
-        update_map_beaglebone(pins, mcu)
-    return pins
-
-# Translate pin names in a firmware command
 re_pin = re.compile(r'(?P<prefix>[ _]pin=)(?P<name>[^ ]*)')
-def update_command(cmd, pmap):
-    def pin_fixup(m):
-        return m.group('prefix') + str(pmap[m.group('name')])
-    return re_pin.sub(pin_fixup, cmd)
+
+class PinResolver:
+    def __init__(self, mcu_type, validate_aliases=True):
+        self.mcu_type = mcu_type
+        self.validate_aliases = validate_aliases
+        self.pins = dict(MCU_PINS.get(mcu_type, {}))
+        self.active_pins = {}
+    def update_aliases(self, mapping_name):
+        self.pins = dict(MCU_PINS.get(self.mcu_type, {}))
+        if mapping_name == 'arduino':
+            update_map_arduino(self.pins, self.mcu_type)
+        elif mapping_name == 'beaglebone':
+            update_map_beaglebone(self.pins, self.mcu_type)
+    def update_command(self, cmd):
+        def pin_fixup(m):
+            name = m.group('name')
+            if name not in self.pins:
+                raise error("Unable to translate pin name: %s" % (cmd,))
+            pin_id = self.pins[name]
+            if (name != self.active_pins.setdefault(pin_id, name)
+                and self.validate_aliases):
+                raise error("pin %s is an alias for %s" % (
+                    name, self.active_pins[pin_id]))
+            return m.group('prefix') + str(pin_id)
+        return re_pin.sub(pin_fixup, cmd)
 
 
 ######################################################################