diff --git a/borgmatic/hooks/monitoring/ntfy.py b/borgmatic/hooks/monitoring/ntfy.py
index 50b31744..e514d679 100644
--- a/borgmatic/hooks/monitoring/ntfy.py
+++ b/borgmatic/hooks/monitoring/ntfy.py
@@ -22,10 +22,14 @@ def initialize_monitor(
     '''
 
 
-def _convert_string_to_array(value):
-    value = str(value or '')
-
-    return [str(item).strip() for item in value.split(',') if str(item).strip()]
+def convert_string_to_array(value):
+    value = '' if value is None else str(value)
+    items = []
+    for item in value.split(','):
+        stripped = item.strip()
+        if stripped:
+            items.append(stripped)
+    return items
 
 
 PRIORITY_NAME_TO_ID = {
@@ -72,7 +76,7 @@ def ping_monitor(hook_config, config, config_filename, state, monitoring_log_lev
             'title': state_config.get('title'),
             'message': state_config.get('message'),
             'priority': PRIORITY_NAME_TO_ID.get(state_config.get('priority'), default_priority),
-            'tags': _convert_string_to_array(state_config.get('tags')),
+            'tags': convert_string_to_array(state_config.get('tags')),
         }
 
         try:
diff --git a/tests/unit/hooks/monitoring/test_ntfy.py b/tests/unit/hooks/monitoring/test_ntfy.py
index 6280785a..17414ad4 100644
--- a/tests/unit/hooks/monitoring/test_ntfy.py
+++ b/tests/unit/hooks/monitoring/test_ntfy.py
@@ -380,3 +380,11 @@ def test_ping_monitor_with_other_error_logs_warning():
         monitoring_log_level=1,
         dry_run=False,
     )
+
+
+def test_convert_string_to_array():
+    assert module.convert_string_to_array(None) == []
+    assert module.convert_string_to_array('') == []
+    assert module.convert_string_to_array('foo') == ['foo']
+    assert module.convert_string_to_array(' foo ,  bar ,baz ') == ['foo', 'bar', 'baz']
+    assert module.convert_string_to_array('foo,,bar,') == ['foo', 'bar']