diff --git a/backend/tools/audit.py b/backend/tools/audit.py
index cf39f16..62279f4 100644
--- a/backend/tools/audit.py
+++ b/backend/tools/audit.py
@@ -7,7 +7,7 @@ Reuses the application audit log (``data/audit.log``, JSON lines) and adds an
 
 from __future__ import annotations
 
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from typing import Any
 
 from backend.audit import _write_entry
@@ -41,7 +41,7 @@ def log_tool_call(
 ) -> None:
     """Append an ``ai_tool_call`` entry to the audit log."""
     _write_entry({
-        "timestamp": datetime.now(timezone.utc).isoformat(),
+        "timestamp": datetime.now(UTC).isoformat(),
         "action": "ai_tool_call",
         "username": username,
         "ip": ip or "unknown",