diff --git a/swh/objstorage/__init__.py b/swh/objstorage/__init__.py
index c62fcf1..c074a00 100644
--- a/swh/objstorage/__init__.py
+++ b/swh/objstorage/__init__.py
@@ -1,75 +1,75 @@
 from .objstorage import ObjStorage
 from .objstorage_pathslicing import PathSlicingObjStorage
 from .api.client import RemoteObjStorage
 from .multiplexer import MultiplexerObjStorage
 from .multiplexer.filter import add_filters
 
 
 __all__ = ['get_objstorage', 'ObjStorage', 'register_objstorages']
 
 
 _STORAGE_CLASSES = {
     'pathslicing': PathSlicingObjStorage,
     'remote': RemoteObjStorage,
 }
 
 
 def register_objstorages(objstorages_map):
     """A function to register new objstorage instances.
 
     This is expected to be called from the client.
 
     Use example:
         from swh.objstorage import register_objstorage, get_objstorage
         from .objstorage_cloud import AwsCloudObjStorage
         from .objstorage_cloud import OpenStackCloudObjStorage
         from .objstorage_azure import AzureCloudObjStorage
 
         objstorage.register_objstorage({
             'aws-storage': AwsCloudObjStorage,
             'openstack-storage': OpenStackCloudObjStorage,
             'azure-storage': AzureCloudObjStorage
         })
 
         # from now on, one can instanciate a new objstorage
         get_objstorage('azure-storage',
                        {'storage-account-name': 'account-name'}...)
 
     """
     _STORAGE_CLASSES.update(objstorages_map)
 
 
 def get_objstorage(cls, args):
     """ Create an ObjStorage using the given implementation class.
 
     Args:
         cls (str): objstorage class unique key contained in the
             _STORAGE_CLASSES dict.
         args (dict): arguments for the required class of objstorage
             that must match exactly the one in the `__init__` method of the
             class.
     Returns:
         subclass of ObjStorage that match the given `storage_class` argument.
     Raises:
         ValueError: if the given storage class is not a valid objstorage
             key.
     """
     try:
         return _STORAGE_CLASSES[cls](**args)
     except KeyError:
-        raise ValueError('Storage class %s does not exists' % cls)
+        raise ValueError('Storage class %s does not exist' % cls)
 
 
 def _construct_filtered_objstorage(storage_conf, filters_conf):
     return add_filters(
         get_objstorage(**storage_conf),
         filters_conf
     )
 _STORAGE_CLASSES['filtered'] = _construct_filtered_objstorage
 
 
 def _construct_multiplexer_objstorage(objstorages):
     storages = [get_objstorage(**conf)
                 for conf in objstorages]
     return MultiplexerObjStorage(storages)
 _STORAGE_CLASSES['multiplexer'] = _construct_multiplexer_objstorage