diff --git a/qubes/app.py b/qubes/app.py
index d9b077f5..caa96b93 100644
--- a/qubes/app.py
+++ b/qubes/app.py
@@ -437,14 +437,17 @@ class VMCollection(object):
 
         raise KeyError(key)
 
-
     def __delitem__(self, key):
         vm = self[key]
+        if not vm.is_halted():
+            msg = "Can't remove, vm {!s}, beacuse it's in state {!s}."
+            msg = msg.format(vm, vm.get_power_state())
+            raise qubes.exc.QubesVMNotHaltedError(msg)
         self.app.fire_event_pre('domain-pre-delete', vm)
+        vm.libvirt_domain.undefine()
         del self._dict[vm.qid]
         self.app.fire_event('domain-delete', vm)
 
-
     def __contains__(self, key):
         return any((key == vm or key == vm.qid or key == vm.name)
                    for vm in self)
diff --git a/qubes/tests/app.py b/qubes/tests/app.py
index 0c81d733..adbe8447 100644
--- a/qubes/tests/app.py
+++ b/qubes/tests/app.py
@@ -24,7 +24,6 @@
 #
 
 import os
-import unittest
 import uuid
 
 import lxml.etree
@@ -42,6 +41,18 @@ class TestVM(qubes.vm.BaseVM):
     netid = qid
     uuid = uuid.uuid5(uuid.NAMESPACE_DNS, 'testvm')
 
+    class MockLibvirt(object):
+        def undefine(self):
+            pass
+
+    libvirt_domain = MockLibvirt()
+
+    def is_halted(self):
+        return True
+
+    def get_power_state(self):
+        return "Halted"
+
 class TestApp(qubes.tests.TestEmitter):
     pass
 
@@ -157,7 +168,7 @@ class TC_90_Qubes(qubes.tests.QubesTestCase):
             os.unlink('/tmp/qubestest.xml')
         except:
             pass
-        app = qubes.Qubes.create_empty_store('/tmp/qubestest.xml')
+        qubes.Qubes.create_empty_store('/tmp/qubestest.xml')
 
     @qubes.tests.skipUnlessGit
     def test_900_example_xml_in_doc(self):
diff --git a/qubes/tests/init.py b/qubes/tests/init.py
index 6969afc0..99105e47 100644
--- a/qubes/tests/init.py
+++ b/qubes/tests/init.py
@@ -23,7 +23,6 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #
 
-import os
 import unittest
 import uuid
 
@@ -70,7 +69,7 @@ class TC_10_property(qubes.tests.QubesTestCase):
         try:
             class MyTestHolder(qubes.tests.TestEmitter, qubes.PropertyHolder):
                 testprop1 = qubes.property('testprop1')
-        except: # pylint: disable=bare-except
+        except:  # pylint: disable=bare-except
             self.skipTest('MyTestHolder class definition failed')
         self.holder = MyTestHolder(None)
 
@@ -120,6 +119,7 @@ class TC_10_property(qubes.tests.QubesTestCase):
             self.assertIs(prop, MyTestHolder.testprop1)
             self.assertEquals(value, 'testvalue')
             return 'settervalue'
+
         class MyTestHolder(qubes.tests.TestEmitter, qubes.PropertyHolder):
             testprop1 = qubes.property('testprop1', setter=setter)
         holder = MyTestHolder(None)
@@ -219,7 +219,6 @@ class TC_20_PropertyHolder(qubes.tests.QubesTestCase):
 
         self.holder = TestHolder(xml)
 
-
     def test_000_property_list(self):
         self.assertListEqual([p.__name__ for p in self.holder.property_list()],
             ['testprop1', 'testprop2', 'testprop3', 'testprop4'])
@@ -293,6 +292,18 @@ class TestVM(qubes.vm.BaseVM):
     netid = qid
     uuid = uuid.uuid5(uuid.NAMESPACE_DNS, 'testvm')
 
+    class MockLibvirt(object):
+        def undefine(self):
+            pass
+
+    libvirt_domain = MockLibvirt()
+
+    def is_halted(self):
+        return True
+
+    def get_power_state(self):
+        return "Halted"
+
 class TestApp(qubes.tests.TestEmitter):
     pass
 
diff --git a/qubes/vm/qubesvm.py b/qubes/vm/qubesvm.py
index e65e78be..96ff4560 100644
--- a/qubes/vm/qubesvm.py
+++ b/qubes/vm/qubesvm.py
@@ -1094,6 +1094,11 @@ class QubesVM(qubes.vm.mix.net.NetVMMixin, qubes.vm.BaseVM):
 
     def remove_from_disk(self):
         '''Remove domain remnants from disk.'''
+        if not self.is_halted():
+            msg = "Can't remove, vm {!s}, beacuse it's in state {!s}."
+            msg = msg.format(self, self.get_power_state())
+            raise qubes.exc.QubesVMNotHaltedError(msg)
+
         self.fire_event('domain-remove-from-disk')
         shutil.rmtree(self.dir_path)
         self.storage.remove()