From d74b340024cad798c3a55c40f442162d76b928a3 Mon Sep 17 00:00:00 2001
From: Dan Helfman <witten@torsion.org>
Date: Sat, 6 Jun 2026 15:31:29 -0700
Subject: [PATCH] Fix a bug in which the "compact" action does not pass a
 compact threshold of zero to Borg.

---
 NEWS                            |  3 +++
 borgmatic/borg/compact.py       |  2 +-
 pyproject.toml                  |  2 +-
 tests/unit/borg/test_compact.py | 16 ++++++++++++++++
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index 2815f5fb..440c8355 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,6 @@
+2.1.7.dev0
+ * Fix a bug in which the "compact" action does not pass a compact threshold of zero to Borg.
+
 2.1.6
  * #1256: Fix a race condition in which borgmatic sometimes swallows Borg error output without
    logging it.
diff --git a/borgmatic/borg/compact.py b/borgmatic/borg/compact.py
index e9ffa99f..d3be5747 100644
--- a/borgmatic/borg/compact.py
+++ b/borgmatic/borg/compact.py
@@ -35,7 +35,7 @@ def compact_segments(
         + (('--lock-wait', str(lock_wait)) if lock_wait else ())
         + (('--progress',) if config.get('progress') else ())
         + (('--cleanup-commits',) if cleanup_commits else ())
-        + (('--threshold', str(threshold)) if threshold else ())
+        + (('--threshold', str(threshold)) if threshold is not None else ())
         + (('--info',) if logger.getEffectiveLevel() == logging.INFO else ())
         + (('--debug', '--show-rc') if logger.isEnabledFor(logging.DEBUG) else ())
         + (
diff --git a/pyproject.toml b/pyproject.toml
index 503bdf80..18135582 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "borgmatic"
-version = "2.1.6"
+version = "2.1.7.dev0"
 authors = [
   { name="Dan Helfman", email="witten@torsion.org" },
 ]
diff --git a/tests/unit/borg/test_compact.py b/tests/unit/borg/test_compact.py
index 5c9b6bfe..1b61960e 100644
--- a/tests/unit/borg/test_compact.py
+++ b/tests/unit/borg/test_compact.py
@@ -229,6 +229,22 @@ def test_compact_segments_with_threshold_calls_borg_with_threshold_flag():
     )
 
 
+def test_compact_segments_with_zero_threshold_calls_borg_with_threshold_flag():
+    flexmock(module.flags).should_receive('make_repository_flags').and_return(('repo',))
+    insert_execute_command_mock(
+        (*COMPACT_COMMAND, '--log-json', '--threshold', '0', 'repo'), logging.INFO
+    )
+    insert_logging_mock(logging.WARNING)
+
+    module.compact_segments(
+        dry_run=False,
+        repository_path='repo',
+        config={'compact_threshold': 0},
+        local_borg_version='1.2.3',
+        global_arguments=flexmock(),
+    )
+
+
 def test_compact_segments_with_umask_calls_borg_with_umask_flags():
     config = {'umask': '077'}
     flexmock(module.flags).should_receive('make_repository_flags').and_return(('repo',))