diff -Nru bolt-0.9.1/debian/changelog bolt-0.9.1/debian/changelog
--- bolt-0.9.1/debian/changelog	2021-01-15 15:17:09.000000000 +0000
+++ bolt-0.9.1/debian/changelog	2021-10-05 06:46:37.000000000 +0000
@@ -1,3 +1,11 @@
+bolt (0.9.1-2) unstable; urgency=medium
+
+  * debian/patches/git_umockdev_update.patch:
+    - Get along with existing mock /sys/{bus,class} directories
+      (Closes: #995248)
+
+ -- Sebastien Bacher <seb128@ubuntu.com>  Tue, 05 Oct 2021 08:46:37 +0200
+
 bolt (0.9.1-1) unstable; urgency=medium
 
   * New bugfix version
diff -Nru bolt-0.9.1/debian/patches/git_umockdev_update.patch bolt-0.9.1/debian/patches/git_umockdev_update.patch
--- bolt-0.9.1/debian/patches/git_umockdev_update.patch	1970-01-01 00:00:00.000000000 +0000
+++ bolt-0.9.1/debian/patches/git_umockdev_update.patch	2021-10-05 06:46:37.000000000 +0000
@@ -0,0 +1,43 @@
+From 130e09d1c7ff02c09e4ad1c9c36e9940b68e58d8 Mon Sep 17 00:00:00 2001
+From: Martin Pitt <martin@piware.de>
+Date: Thu, 16 Sep 2021 10:10:03 +0200
+Subject: [PATCH] tests/mock: Get along with existing mock /sys/{bus,class}
+ directories
+
+This was fixed in umockdev 0.16.3, but now causes warning messages due
+to the existing directories. This at least breaks Debian/Ubuntu's
+autopkgtests.
+---
+ tests/mock-sysfs.c | 8 +++++---
+ 1 file changed, 5 insertions(+), 3 deletions(-)
+
+diff --git a/tests/mock-sysfs.c b/tests/mock-sysfs.c
+index 6d0df1d..9d08430 100644
+--- a/tests/mock-sysfs.c
++++ b/tests/mock-sysfs.c
+@@ -175,19 +175,21 @@ mock_sysfs_init (MockSysfs *ms)
+   ms->devices = g_hash_table_new (g_str_hash, g_str_equal);
+ 
+   /* udev_enumerate_scan_devices() will return -ENOENT, if
+-   * sys/bus or sys/class directories can not be found
++   * sys/bus or sys/class directories can not be found;
++   * fixed in https://github.com/martinpitt/umockdev/commit/5e8296014346
++   * but work with older versions as well
+    */
+   sys = umockdev_testbed_get_sys_dir (ms->bed);
+ 
+   bus = g_build_filename (sys, "bus", NULL);
+   r = g_mkdir (bus, 0744);
+ 
+-  if (r < 0)
++  if (r < 0 && errno != EEXIST)
+     g_warning ("could not create %s", bus);
+ 
+   cls = g_build_filename (sys, "class", NULL);
+   r = g_mkdir (cls, 0744);
+-  if (r < 0)
++  if (r < 0 && errno != EEXIST)
+     g_warning ("could not create %s", bus);
+ }
+ 
+-- 
diff -Nru bolt-0.9.1/debian/patches/series bolt-0.9.1/debian/patches/series
--- bolt-0.9.1/debian/patches/series	2021-01-15 15:17:09.000000000 +0000
+++ bolt-0.9.1/debian/patches/series	2021-10-05 06:46:37.000000000 +0000
@@ -0,0 +1 @@
+git_umockdev_update.patch