diff --git a/mempalace/mcp_server.py b/mempalace/mcp_server.py
index 3918a19..7cac8f0 100644
--- a/mempalace/mcp_server.py
+++ b/mempalace/mcp_server.py
@@ -925,6 +925,7 @@ def tool_diary_write(agent_name: str, entry: str, topic: str = "general"):
     try:
         agent_name = sanitize_name(agent_name, "agent_name")
         entry = sanitize_content(entry)
+        topic = sanitize_name(topic, "topic")
     except ValueError as e:
         return {"success": False, "error": str(e)}