diff -pruN 4.0.0-1/debian/changelog 4.0.0-1ubuntu1/debian/changelog
--- 4.0.0-1/debian/changelog	2022-09-29 12:31:47.000000000 +0000
+++ 4.0.0-1ubuntu1/debian/changelog	2023-03-07 02:53:47.000000000 +0000
@@ -1,3 +1,9 @@
+libthread-pool (4.0.0-1ubuntu1) lunar; urgency=medium
+
+  * debian/patches/fix-unsigned-cast.patch: fix FTBS for armhf (LP: #2009537).
+
+ -- Vladimir Petko <vladimir.petko@canonical.com>  Tue, 07 Mar 2023 15:53:47 +1300
+
 libthread-pool (4.0.0-1) unstable; urgency=medium
 
   [ Nilesh Patra ]
diff -pruN 4.0.0-1/debian/control 4.0.0-1ubuntu1/debian/control
--- 4.0.0-1/debian/control	2022-09-29 12:31:47.000000000 +0000
+++ 4.0.0-1ubuntu1/debian/control	2023-03-07 02:53:47.000000000 +0000
@@ -1,5 +1,6 @@
 Source: libthread-pool
-Maintainer: Debian Med Packaging Team <debian-med-packaging@lists.alioth.debian.org>
+Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
+XSBC-Original-Maintainer: Debian Med Packaging Team <debian-med-packaging@lists.alioth.debian.org>
 Uploaders: Andreas Tille <tille@debian.org>
 Section: science
 Priority: optional
diff -pruN 4.0.0-1/debian/patches/fix-unsigned-cast.patch 4.0.0-1ubuntu1/debian/patches/fix-unsigned-cast.patch
--- 4.0.0-1/debian/patches/fix-unsigned-cast.patch	1970-01-01 00:00:00.000000000 +0000
+++ 4.0.0-1ubuntu1/debian/patches/fix-unsigned-cast.patch	2023-03-07 02:53:47.000000000 +0000
@@ -0,0 +1,19 @@
+Description: Use size_t type for max() comparison
+ size_t is defined in an architecture-specific way. Construct size_t from int to avoid
+ the type mismatch error.
+Author: Vladimir Petko <vladimir.petko@canonical.com>
+Bug: https://github.com/rvaser/thread_pool/pull/6
+Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1032532
+Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/libthread-pool/+bug/2009537
+Last-Update: 2023-03-08
+--- a/include/thread_pool/thread_pool.hpp
++++ b/include/thread_pool/thread_pool.hpp
+@@ -24,7 +24,7 @@
+       std::size_t num_threads = std::thread::hardware_concurrency())
+       : threads_(),
+         thread_map_(),
+-        queues_(std::max(1UL, num_threads)),
++        queues_(std::max(size_t(1), num_threads)),
+         task_id_(0) {
+     for (std::size_t i = 0; i != queues_.size(); ++i) {
+       threads_.emplace_back([this, i] () -> void { Task(i); });
diff -pruN 4.0.0-1/debian/patches/series 4.0.0-1ubuntu1/debian/patches/series
--- 4.0.0-1/debian/patches/series	1970-01-01 00:00:00.000000000 +0000
+++ 4.0.0-1ubuntu1/debian/patches/series	2023-03-07 02:53:47.000000000 +0000
@@ -0,0 +1 @@
+fix-unsigned-cast.patch