diff --git a/src/osmium/replication/utils.py b/src/osmium/replication/utils.py
index ef67ca1..dd41f5f 100644
--- a/src/osmium/replication/utils.py
+++ b/src/osmium/replication/utils.py
@@ -57,7 +57,7 @@ def get_replication_header(fname: str) -> ReplicationHeader:
                     LOG.warning("Sequence id '%d' in OSM file header is negative. Ignored.", seq)
                     seq = None
             except ValueError:
-                LOG.warning("Sequence id '%s' in OSM file header is not a number. Ignored.", seq)
+                LOG.warning("Sequence id '%s' in OSM file header is not a number. Ignored.", seqstr)
                 seq = None
         else:
             seq = None
diff --git a/test/test_replication_utils.py b/test/test_replication_utils.py
index eff4a0a..1db9f03 100644
--- a/test/test_replication_utils.py
+++ b/test/test_replication_utils.py
@@ -4,6 +4,8 @@
 #
 # Copyright (C) 2025 Sarah Hoffmann <lonvia@denofr.de> and others.
 # For a full list of authors see the git log.
+import logging
+
 import osmium.replication.utils as rutil
 
 from helpers import mkdate
@@ -25,3 +27,49 @@ def test_get_replication_header_full(test_data_dir):
     assert val.url == 'http://download.geofabrik.de/europe/andorra-updates'
     assert val.sequence == 2167
     assert val.timestamp == mkdate(2019, 2, 23, 21, 15, 2)
+
+
+def test_get_replication_header_invalid_sequence(caplog):
+    from unittest.mock import MagicMock, patch
+
+    mock_header = MagicMock()
+    mock_header.get.side_effect = lambda k: {
+        "osmosis_replication_base_url": "https://example.com/replication",
+        "osmosis_replication_sequence_number": "not-a-number",
+        "osmosis_replication_timestamp": "2024-01-01T00:00:00Z",
+    }.get(k)
+
+    mock_reader = MagicMock()
+    mock_reader.header.return_value = mock_header
+
+    with patch('osmium.replication.utils.oreader', return_value=mock_reader):
+        with caplog.at_level(logging.WARNING, logger='pyosmium'):
+            val = rutil.get_replication_header('dummy.pbf')
+
+    assert val.url == 'https://example.com/replication'
+    assert val.sequence is None
+    assert val.timestamp is not None
+    assert 'not-a-number' in caplog.text
+
+
+def test_get_replication_header_negative_sequence(caplog):
+    from unittest.mock import MagicMock, patch
+
+    mock_header = MagicMock()
+    mock_header.get.side_effect = lambda k: {
+        "osmosis_replication_base_url": "https://example.com/replication",
+        "osmosis_replication_sequence_number": "-5",
+        "osmosis_replication_timestamp": "2024-01-01T00:00:00Z",
+    }.get(k)
+
+    mock_reader = MagicMock()
+    mock_reader.header.return_value = mock_header
+
+    with patch('osmium.replication.utils.oreader', return_value=mock_reader):
+        with caplog.at_level(logging.WARNING, logger='pyosmium'):
+            val = rutil.get_replication_header('dummy.pbf')
+
+    assert val.url == 'https://example.com/replication'
+    assert val.sequence is None
+    assert val.timestamp is not None
+    assert '-5' in caplog.text