diff --git a/integrations/opensearch/src/haystack_integrations/document_stores/opensearch/document_store.py b/integrations/opensearch/src/haystack_integrations/document_stores/opensearch/document_store.py
index 496d22ea0..71befb2fe 100644
--- a/integrations/opensearch/src/haystack_integrations/document_stores/opensearch/document_store.py
+++ b/integrations/opensearch/src/haystack_integrations/document_stores/opensearch/document_store.py
@@ -119,10 +119,15 @@ def client(self) -> OpenSearch:
         elif self._create_index:
             # Create the index if it doesn't exist
             body = {"mappings": self._mappings, "settings": self._settings}
-            self._client.indices.create(index=self._index, body=body)
+            self._client.indices.create(index=self._index, body=body)  # type:ignore
         return self._client
-    
-    def create_index(self, index: Optional[str] = None, mappings: Optional[Dict[str, Any]] = None, settings: Optional[Dict[str, Any]] = None) -> None:
+
+    def create_index(
+        self,
+        index: Optional[str] = None,
+        mappings: Optional[Dict[str, Any]] = None,
+        settings: Optional[Dict[str, Any]] = None,
+    ) -> None:
         """
         Creates an index in OpenSearch.
 
@@ -141,7 +146,7 @@ def create_index(self, index: Optional[str] = None, mappings: Optional[Dict[str,
             mappings = self._mappings
         if not settings:
             settings = self._settings
-        
+
         if not self.client.indices.exists(index=index):
             self.client.indices.create(index=index, body={"mappings": mappings, "settings": settings})
 
diff --git a/integrations/opensearch/tests/test_document_store.py b/integrations/opensearch/tests/test_document_store.py
index 024ff94f1..51fc23a6e 100644
--- a/integrations/opensearch/tests/test_document_store.py
+++ b/integrations/opensearch/tests/test_document_store.py
@@ -207,7 +207,7 @@ def test_write_documents_readonly(self, document_store_readonly: OpenSearchDocum
 
     def test_create_index(self, document_store_readonly: OpenSearchDocumentStore):
         document_store_readonly.create_index()
-        assert document_store_readonly.client.indices.exists(index=document_store_readonly.index)
+        assert document_store_readonly.client.indices.exists(index=document_store_readonly._index)
 
     def test_bm25_retrieval(self, document_store: OpenSearchDocumentStore):
         document_store.write_documents(