diff --git a/nova/tests/unit/virt/disk/vfs/test_guestfs.py b/nova/tests/unit/virt/disk/vfs/test_guestfs.py
index 9cb879f70959..d0bd542ccfce 100644
--- a/nova/tests/unit/virt/disk/vfs/test_guestfs.py
+++ b/nova/tests/unit/virt/disk/vfs/test_guestfs.py
@@ -335,7 +335,8 @@ class VirtDiskVFSGuestFSTest(test.NoDBTestCase):
         m.launch.side_effect = Exception
         vfs = vfsimpl.VFSGuestFS(self.qcowfile)
         mock_access.return_value = False
-        with mock.patch('eventlet.tpool.Proxy', return_value=m):
+        self.flags(debug=False, group='guestfs')
+        with mock.patch('eventlet.tpool.Proxy', return_value=m) as tpool_mock:
             self.assertRaises(exception.LibguestfsCannotReadKernel,
                                     vfs.inspect_capabilities)
             m.add_drive.assert_called_once_with('/dev/null')
@@ -343,3 +344,17 @@ class VirtDiskVFSGuestFSTest(test.NoDBTestCase):
             mock_access.assert_called_once_with('/boot/vmlinuz-kernel_name',
                                                 mock.ANY)
             mock_uname.assert_called_once_with()
+            self.assertEqual(1, tpool_mock.call_count)
+
+    def test_appliance_setup_inspect_capabilties_debug_mode(self):
+        """Asserts that we do not use an eventlet thread pool when guestfs
+        debug logging is enabled.
+        """
+        # We can't actually mock guestfs.GuestFS because it's an optional
+        # native package import. All we really care about here is that
+        # eventlet isn't used.
+        self.flags(debug=True, group='guestfs')
+        vfs = vfsimpl.VFSGuestFS(self.qcowfile)
+        with mock.patch('eventlet.tpool.Proxy',
+                        new_callable=mock.NonCallableMock):
+            vfs.inspect_capabilities()
diff --git a/nova/virt/disk/vfs/guestfs.py b/nova/virt/disk/vfs/guestfs.py
index 6e848bb72d82..84dddd875f37 100644
--- a/nova/virt/disk/vfs/guestfs.py
+++ b/nova/virt/disk/vfs/guestfs.py
@@ -75,7 +75,14 @@ class VFSGuestFS(vfs.VFS):
     def inspect_capabilities(self):
         """Determines whether guestfs is well configured."""
         try:
-            g = tpool.Proxy(guestfs.GuestFS())
+            # If guestfs debug is enabled, we can't launch in a thread because
+            # the debug logging callback can make eventlet try to switch
+            # threads and then the launch hangs, causing eternal sadness.
+            if CONF.guestfs.debug:
+                LOG.debug('Inspecting guestfs capabilities non-threaded.')
+                g = guestfs.GuestFS()
+            else:
+                g = tpool.Proxy(guestfs.GuestFS())
             g.add_drive("/dev/null")  # sic
             g.launch()
         except Exception as e: