diff --git a/gpiozero/output_devices.py b/gpiozero/output_devices.py
index 1b3c2e2..e516911 100644
--- a/gpiozero/output_devices.py
+++ b/gpiozero/output_devices.py
@@ -142,14 +142,17 @@ class DigitalOutputDevice(OutputDevice):
 
     def close(self):
         self._stop_blink()
+        self._stop_source()
         super(DigitalOutputDevice, self).close()
 
     def on(self):
         self._stop_blink()
+        self._stop_source()
         self._write(True)
 
     def off(self):
         self._stop_blink()
+        self._stop_source()
         self._write(False)
 
     def blink(self, on_time=1, off_time=1, n=None, background=True):
@@ -172,6 +175,7 @@ class DigitalOutputDevice(OutputDevice):
             this method never returning).
         """
         self._stop_blink()
+        self._stop_source()
         self._blink_thread = GPIOThread(
             target=self._blink_device, args=(on_time, off_time, n)
         )
@@ -180,6 +184,10 @@ class DigitalOutputDevice(OutputDevice):
             self._blink_thread.join()
             self._blink_thread = None
 
+    def _stop_source(self):
+        if self.source is not None:
+            self.source = None
+
     def _stop_blink(self):
         if self._controller:
             self._controller._stop_blink(self)
@@ -1207,4 +1215,3 @@ class AngularServo(Servo):
                 self._value_range *
                 ((value - self._min_angle) / self._angular_range) +
                 self._min_value)
-