diff --git a/backend/main.py b/backend/main.py
index 1ca47dc..df86d6b 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -439,7 +439,7 @@ def extract_entities_with_llm(text: str) -> tuple[List[dict], List[dict]]:
     
     return [], []
 
-def align_entity(project_id: str, name: str, db, definition: str = "") -> Optional[Entity]:
+def align_entity(project_id: str, name: str, db, definition: str = "") -> Optional['Entity']:
     """实体对齐 - Phase 3: 使用 embedding 对齐"""
     # 1. 首先尝试精确匹配
     existing = db.get_entity_by_name(project_id, name)