diff --git a/graphrag/index/utils/hashing.py b/graphrag/index/utils/hashing.py
index 4ee6a98bbf..94f121a0d9 100644
--- a/graphrag/index/utils/hashing.py
+++ b/graphrag/index/utils/hashing.py
@@ -8,7 +8,7 @@
 from typing import Any
 
 
-def gen_sha512_hash(item: dict[str, Any], hashcode: Iterable[str]):
+def gen_sha512_hash(item: dict[str, Any], hashcode: Iterable[str]) -> str:
     """Generate a SHA512 hash."""
     hashed = "".join([str(item[column]) for column in hashcode])
     return f"{sha512(hashed.encode('utf-8'), usedforsecurity=False).hexdigest()}"