diff --git a/libs/core/langchain_core/indexing/in_memory.py b/libs/core/langchain_core/indexing/in_memory.py
index 10b0e087d04..0279044e5c9 100644
--- a/libs/core/langchain_core/indexing/in_memory.py
+++ b/libs/core/langchain_core/indexing/in_memory.py
@@ -23,9 +23,9 @@ class InMemoryDocumentIndexer(DocumentIndexer):
 
         for item in items:
             if item.id is None:
-                id_ = uuid.uuid4()
+                id_ = str(uuid.uuid4())
                 item_ = item.copy()
-                item_.id = str(id_)
+                item_.id = id_
             else:
                 item_ = item
                 id_ = item.id
diff --git a/libs/core/tests/unit_tests/indexing/test_in_memory_indexer.py b/libs/core/tests/unit_tests/indexing/test_in_memory_indexer.py
index 4f6ceadb162..bb3a1e2ce32 100644
--- a/libs/core/tests/unit_tests/indexing/test_in_memory_indexer.py
+++ b/libs/core/tests/unit_tests/indexing/test_in_memory_indexer.py
@@ -1,6 +1,6 @@
 """Test in memory indexer"""
 
-from typing import Generator
+from typing import Generator, AsyncGenerator
 
 import pytest
 from langchain_standard_tests.integration_tests.indexer import (
@@ -23,5 +23,5 @@ class TestDocumentIndexerTestSuite(DocumentIndexerTestSuite):
 
 class TestAsyncDocumentIndexerTestSuite(AsyncDocumentIndexerTestSuite):
     @pytest.fixture()
-    async def indexer(self) -> Generator[AsyncDocumentIndexer, None, None]:
+    async def indexer(self) -> AsyncGenerator[AsyncDocumentIndexer, None]:
         yield AsyncInMemoryDocumentIndexer()