diff --git a/qubes/devices.py b/qubes/devices.py
index a0838ff0..91f38fc0 100644
--- a/qubes/devices.py
+++ b/qubes/devices.py
@@ -270,6 +270,27 @@ class DeviceCollection(object):
         device_assignment.bus = self._bus
         self._set.add(device_assignment)
 
+    def update_persistent(self, device: DeviceInfo, persistent: bool):
+        '''Update `persistent` flag of already attached device.
+        '''
+
+        if self._vm.is_halted():
+            raise qubes.exc.QubesVMNotStartedError(self._vm,
+                'VM must be running to modify device persistence flag')
+        assignments = [a for a in self.assignments() if a.device == device]
+        if not assignments:
+            raise qubes.exc.QubesValueError('Device not assigned')
+        assert len(assignments) == 1
+        assignment = assignments[0]
+
+        # be careful to use already present assignment, not the provided one
+        # - to not change options as a side effect
+        if persistent and device not in self._set:
+            assignment.persistent = True
+            self._set.add(assignment)
+        elif not persistent and device in self._set:
+            self._set.discard(assignment)
+
     @asyncio.coroutine
     def detach(self, device_assignment: DeviceAssignment):
         '''Detach (remove) device from domain.
diff --git a/qubes/tests/devices.py b/qubes/tests/devices.py
index 3433eba2..c436ea3e 100644
--- a/qubes/tests/devices.py
+++ b/qubes/tests/devices.py
@@ -71,6 +71,9 @@ class TestVM(qubes.tests.TestEmitter):
     def is_halted(self):
         return not self.running
 
+    def is_running(self):
+        return self.running
+
 
 
 class TC_00_DeviceCollection(qubes.tests.QubesTestCase):
@@ -130,8 +133,6 @@ class TC_00_DeviceCollection(qubes.tests.QubesTestCase):
         self.loop.run_until_complete(self.collection.attach(self.assignment))
         self.assertEventFired(self.emitter, 'device-list-attached:testclass')
         self.assertEqual({self.device}, set(self.collection.persistent()))
-        self.assertEqual({self.device},
-            set(self.collection.persistent()))
         self.assertEqual(set([]),
             set(self.collection.attached()))
 
@@ -153,6 +154,52 @@ class TC_00_DeviceCollection(qubes.tests.QubesTestCase):
         self.assertEqual({self.device}, set(self.collection))
         self.assertEventFired(self.emitter, 'device-list:testclass')
 
+    def test_020_update_persistent_to_false(self):
+        self.emitter.running = True
+        self.assertEqual(set([]), set(self.collection.persistent()))
+        self.loop.run_until_complete(self.collection.attach(self.assignment))
+        # device-attach event not implemented, so manipulate object manually
+        self.device.frontend_domain = self.emitter
+        self.assertEqual({self.device}, set(self.collection.persistent()))
+        self.assertEqual({self.device}, set(self.collection.attached()))
+        self.assertEqual({self.device}, set(self.collection.persistent()))
+        self.assertEqual({self.device}, set(self.collection.attached()))
+        self.collection.update_persistent(self.device, False)
+        self.assertEqual(set(), set(self.collection.persistent()))
+        self.assertEqual({self.device}, set(self.collection.attached()))
+
+    def test_021_update_persistent_to_true(self):
+        self.assignment.persistent = False
+        self.emitter.running = True
+        self.assertEqual(set([]), set(self.collection.persistent()))
+        self.loop.run_until_complete(self.collection.attach(self.assignment))
+        # device-attach event not implemented, so manipulate object manually
+        self.device.frontend_domain = self.emitter
+        self.assertEqual(set(), set(self.collection.persistent()))
+        self.assertEqual({self.device}, set(self.collection.attached()))
+        self.assertEqual(set(), set(self.collection.persistent()))
+        self.assertEqual({self.device}, set(self.collection.attached()))
+        self.collection.update_persistent(self.device, True)
+        self.assertEqual({self.device}, set(self.collection.persistent()))
+        self.assertEqual({self.device}, set(self.collection.attached()))
+
+    def test_022_update_persistent_reject_not_running(self):
+        self.assertEqual(set([]), set(self.collection.persistent()))
+        self.loop.run_until_complete(self.collection.attach(self.assignment))
+        self.assertEqual({self.device}, set(self.collection.persistent()))
+        self.assertEqual(set(), set(self.collection.attached()))
+        with self.assertRaises(qubes.exc.QubesVMNotStartedError):
+            self.collection.update_persistent(self.device, False)
+
+    def test_023_update_persistent_reject_not_attached(self):
+        self.assertEqual(set(), set(self.collection.persistent()))
+        self.assertEqual(set(), set(self.collection.attached()))
+        self.emitter.running = True
+        with self.assertRaises(qubes.exc.QubesValueError):
+            self.collection.update_persistent(self.device, True)
+        with self.assertRaises(qubes.exc.QubesValueError):
+            self.collection.update_persistent(self.device, False)
+
 
 class TC_01_DeviceManager(qubes.tests.QubesTestCase):
     def setUp(self):