diff --git a/gpiozero/input_devices.py b/gpiozero/input_devices.py
index be2afd1..2d7f27a 100644
--- a/gpiozero/input_devices.py
+++ b/gpiozero/input_devices.py
@@ -13,13 +13,17 @@ class InputDevice(object):
         if pin is None:
             raise InputDeviceError('No GPIO pin number given')
 
-        self.pin = pin
+        self._pin = pin
         self._pull = GPIO.PUD_UP
         self._edge = GPIO.FALLING
         self._active_state = 0
         self._inactive_state = 1
         GPIO.setup(pin, GPIO.IN, self._pull)
 
+    @property
+    def pin(self):
+        return self._pin
+
     @property
     def is_active(self):
         return GPIO.input(self.pin) == self._active_state
@@ -77,9 +81,13 @@ class LightSensor(object):
         if pin is None:
             raise InputDeviceError('No GPIO pin number given')
 
-        self.pin = pin
+        self._pin = pin
         self.darkness_level = darkness_level
 
+    @property
+    def pin(self):
+        return self._pin
+
     @property
     def value(self):
         return self._get_average_light_level(5)