diff --git a/src/borg/repository.py b/src/borg/repository.py
index cddbcf745..ccfbf6e59 100644
--- a/src/borg/repository.py
+++ b/src/borg/repository.py
@@ -987,13 +987,14 @@ class Repository:
         # pack-sizing overrides: BORG_PACK_MAX_COUNT sets the max object count per pack,
         # BORG_PACK_MAX_SIZE the max pack size in bytes. Default: size-bound only.
         # They are validated here, so a bad value fails before the store is created, opened or locked.
-        # A non-integer or non-positive value is rejected. The size must also stay below
+        # An empty value counts as unset, like BORG_PACK_CACHE_SIZE. A non-integer or non-positive
+        # value is rejected. The size must also stay below
         # MAX_PACK_SIZE_LIMIT: add() keeps the object that crosses the cap, so this keeps packs
         # below 2 GiB, clear of OS bugs with files of 2 GiB or more. Count-only mode still passes
         # that ceiling (minus one) as max_size. pack_max_size remembers the configured size, or the
         # default when the user did not set one, so the safety ceiling does not become the compact target.
-        max_count_env = os.environ.get("BORG_PACK_MAX_COUNT")
-        max_size_env = os.environ.get("BORG_PACK_MAX_SIZE")
+        max_count_env = os.environ.get("BORG_PACK_MAX_COUNT") or None
+        max_size_env = os.environ.get("BORG_PACK_MAX_SIZE") or None
         if max_count_env is None:
             max_count = None
         else:
diff --git a/src/borg/testsuite/repository_test.py b/src/borg/testsuite/repository_test.py
index 39ae7c95c..9bd170605 100644
--- a/src/borg/testsuite/repository_test.py
+++ b/src/borg/testsuite/repository_test.py
@@ -1454,7 +1454,7 @@ class FailingPackStore:
         return getattr(self._inner, name)
 
 
-@pytest.mark.parametrize("value", ["0", "-1", "abc", str(MAX_PACK_SIZE_LIMIT), ""])
+@pytest.mark.parametrize("value", ["0", "-1", "abc", str(MAX_PACK_SIZE_LIMIT)])
 def test_borg_pack_max_size_rejected(tmp_path, monkeypatch, value):
     with Repository(os.fspath(tmp_path / "repo"), exclusive=True, create=True) as repository:
         pass
@@ -1483,7 +1483,7 @@ def test_borg_pack_max_size_just_below_limit(tmp_path, monkeypatch):
         assert repository.pack_max_size == accepted
 
 
-@pytest.mark.parametrize("value", ["0", "-1", "nope", ""])
+@pytest.mark.parametrize("value", ["0", "-1", "nope"])
 def test_borg_pack_max_count_rejected(tmp_path, monkeypatch, value):
     with Repository(os.fspath(tmp_path / "repo"), exclusive=True, create=True) as repository:
         pass
@@ -1515,6 +1515,17 @@ def test_borg_pack_limits_default_when_unset(tmp_path, monkeypatch):
         assert repository.pack_max_size == DEFAULT_PACK_MAX_SIZE
 
 
+def test_borg_pack_limits_empty_means_unset(tmp_path, monkeypatch):
+    with Repository(os.fspath(tmp_path / "repo"), exclusive=True, create=True) as repository:
+        pass
+    monkeypatch.setenv("BORG_PACK_MAX_COUNT", "")
+    monkeypatch.setenv("BORG_PACK_MAX_SIZE", "")
+    with reopen(repository) as repository:
+        assert repository._pack_writer.max_count is None
+        assert repository._pack_writer.max_size == DEFAULT_PACK_MAX_SIZE
+        assert repository.pack_max_size == DEFAULT_PACK_MAX_SIZE
+
+
 def test_borg_pack_count_and_size_both_passed_through(tmp_path, monkeypatch):
     with Repository(os.fspath(tmp_path / "repo"), exclusive=True, create=True) as repository:
         pass