diff --git a/qubes/storage/lvm.py b/qubes/storage/lvm.py
index 778de397..2d35f2fe 100644
--- a/qubes/storage/lvm.py
+++ b/qubes/storage/lvm.py
@@ -227,6 +227,8 @@ class ThinVolume(qubes.storage.Volume):
     @property
     def size(self):
         try:
+            if self.is_dirty():
+                return qubes.storage.lvm.size_cache[self._vid_snap]['size']
             return qubes.storage.lvm.size_cache[self.vid]['size']
         except KeyError:
             return self._size
@@ -427,18 +429,19 @@ class ThinVolume(qubes.storage.Volume):
         if size < self.size:
             raise qubes.storage.StoragePoolException(
                 'For your own safety, shrinking of %s is'
-                ' disabled. If you really know what you'
+                ' disabled (%d < %d). If you really know what you'
                 ' are doing, use `lvresize` on %s manually.' %
-                (self.name, self.vid))
+                (self.name, size, self.size, self.vid))
 
         if size == self.size:
             return
 
-        cmd = ['extend', self.vid, str(size)]
-        qubes_lvm(cmd, self.log)
         if self.is_dirty():
             cmd = ['extend', self._vid_snap, str(size)]
             qubes_lvm(cmd, self.log)
+        elif self.save_on_stop or not self.snap_on_start:
+            cmd = ['extend', self.vid, str(size)]
+            qubes_lvm(cmd, self.log)
         reset_cache()
 
     def _snapshot(self):
diff --git a/qubes/tests/storage_lvm.py b/qubes/tests/storage_lvm.py
index f6a4be69..2672a280 100644
--- a/qubes/tests/storage_lvm.py
+++ b/qubes/tests/storage_lvm.py
@@ -178,6 +178,60 @@ class TC_00_ThinPool(ThinPoolBase):
         pool_usage = float(pool_usage)
         self.assertEqual(usage, int(pool_size * pool_usage / 100))
 
+    def _get_size(self, path):
+        if os.getuid() != 0:
+            return int(
+                subprocess.check_output(
+                    ['sudo', 'blockdev', '--getsize64', path]))
+        fd = os.open(path, os.O_RDONLY)
+        try:
+            return os.lseek(fd, 0, os.SEEK_END)
+        finally:
+            os.close(fd)
+
+    def test_006_resize(self):
+        config = {
+            'name': 'root',
+            'pool': self.pool.name,
+            'rw': True,
+            'save_on_stop': True,
+            'size': 32 * 1024**2,
+        }
+        vm = qubes.tests.storage.TestVM(self)
+        volume = self.app.get_pool(self.pool.name).init_volume(vm, config)
+        volume.create()
+        self.addCleanup(volume.remove)
+        path = "/dev/%s" % volume.vid
+        new_size = 64 * 1024 ** 2
+        volume.resize(new_size)
+        self.assertEqual(self._get_size(path), new_size)
+        self.assertEqual(volume.size, new_size)
+
+    def test_007_resize_running(self):
+        old_size = 32 * 1024**2
+        config = {
+            'name': 'root',
+            'pool': self.pool.name,
+            'rw': True,
+            'save_on_stop': True,
+            'size': old_size,
+        }
+        vm = qubes.tests.storage.TestVM(self)
+        volume = self.app.get_pool(self.pool.name).init_volume(vm, config)
+        volume.create()
+        self.addCleanup(volume.remove)
+        volume.start()
+        path = "/dev/%s" % volume.vid
+        path2 = "/dev/%s" % volume._vid_snap
+        new_size = 64 * 1024 ** 2
+        volume.resize(new_size)
+        self.assertEqual(self._get_size(path), old_size)
+        self.assertEqual(self._get_size(path2), new_size)
+        self.assertEqual(volume.size, new_size)
+        volume.stop()
+        self.assertEqual(self._get_size(path), new_size)
+        self.assertEqual(volume.size, new_size)
+
 
 @skipUnlessLvmPoolExists
 class TC_01_ThinPool(ThinPoolBase, qubes.tests.SystemTestCase):