diff --git a/fastapi/applications.py b/fastapi/applications.py
index 02193312b..740c3ed79 100644
--- a/fastapi/applications.py
+++ b/fastapi/applications.py
@@ -289,6 +289,7 @@ class FastAPI(Starlette):
                 """
             ),
         ] = None,
+        openapi_response_class: Type[JSONResponse] = JSONResponse,
         servers: Annotated[
             Optional[List[Dict[str, Union[str, Any]]]],
             Doc(
@@ -865,6 +866,7 @@ class FastAPI(Starlette):
         self.license_info = license_info
         self.openapi_url = openapi_url
         self.openapi_tags = openapi_tags
+        self.openapi_response_class = openapi_response_class
         self.root_path_in_servers = root_path_in_servers
         self.docs_url = docs_url
         self.redoc_url = redoc_url
@@ -1091,7 +1093,7 @@ class FastAPI(Starlette):
                     if root_path and self.root_path_in_servers:
                         self.servers.insert(0, {"url": root_path})
                         server_urls.add(root_path)
-                return JSONResponse(self.openapi())
+                return self.openapi_response_class(self.openapi())
 
             self.add_route(self.openapi_url, openapi, include_in_schema=False)
         if self.openapi_url and self.docs_url: