diff --git a/swh/core/api/__init__.py b/swh/core/api/__init__.py
--- a/swh/core/api/__init__.py
+++ b/swh/core/api/__init__.py
@@ -313,9 +313,10 @@
                  **kwargs):
         super().__init__(*args, **kwargs)
 
+        self.backend_class = backend_class
         if backend_class is not None:
             if backend_factory is None:
-                raise TypeError('Missing argument backend_factory')
+                backend_factory = backend_class
             for (meth_name, meth) in backend_class.__dict__.items():
                 if hasattr(meth, '_endpoint_path'):
                     self.__add_endpoint(meth_name, meth, backend_factory)