diff --git a/swh/model/cli.py b/swh/model/cli.py
index 82af76f..b1dcd9a 100644
--- a/swh/model/cli.py
+++ b/swh/model/cli.py
@@ -1,125 +1,125 @@
 # Copyright (C) 2018  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import click
 import os
 import sys
 
 from functools import partial
 
 from swh.model import identifiers as pids
 from swh.model.exceptions import ValidationError
 from swh.model.from_disk import Content, Directory
 
 
 class PidParamType(click.ParamType):
     name = 'persistent identifier'
 
     def convert(self, value, param, ctx):
         try:
             pids.parse_persistent_identifier(value)
             return value  # return as string, as we need just that
         except ValidationError as e:
             self.fail('%s is not a valid PID. %s.' % (value, e), param, ctx)
 
 
 def pid_of_file(path):
     object = Content.from_file(path=path).get_data()
     return pids.persistent_identifier(pids.CONTENT, object)
 
 
 def pid_of_dir(path):
     object = Directory.from_disk(path=path).get_data()
     return pids.persistent_identifier(pids.DIRECTORY, object)
 
 
 def identify_object(obj_type, follow_symlinks, obj):
     if obj_type == 'auto':
         if os.path.isfile(obj):
             obj_type = 'content'
         elif os.path.isdir(obj):
             obj_type = 'directory'
         else:  # shouldn't happen, due to path validation
             raise click.BadParameter('%s is neither a file nor a directory' %
                                      obj)
 
     path = obj
     if follow_symlinks and os.path.islink(obj):
         path = os.path.realpath(obj)
 
     pid = None
     if obj_type == 'content':
         pid = pid_of_file(path)
     elif obj_type == 'directory':
         pid = pid_of_dir(path)
     else:  # shouldn't happen, due to option validation
         raise click.BadParameter('invalid object type: ' + obj_type)
 
     # note: we return original obj instead of path here, to preserve user-given
     # file name in output
     return (obj, pid)
 
 
 @click.command()
 @click.option('--dereference/--no-dereference', 'follow_symlinks',
               default=True,
               help='follow (or not) symlinks for OBJECTS passed as arguments '
               + '(default: follow)')
 @click.option('--filename/--no-filename', 'show_filename', default=True,
               help='show/hide file name (default: show)')
 @click.option('--type', '-t', 'obj_type', default='auto',
               type=click.Choice(['auto', 'content', 'directory']),
               help='type of object to identify (default: auto)')
 @click.option('--verify', '-v', metavar='PID', type=PidParamType(),
               help='reference identifier to be compared with computed one')
-@click.argument('objects', nargs=-1,
+@click.argument('objects', nargs=-1, required=True,
                 type=click.Path(exists=True, readable=True,
                                 allow_dash=True, path_type=bytes))
 def identify(obj_type, verify, show_filename, follow_symlinks, objects):
     """Compute the Software Heritage persistent identifier (PID) for the given
     source code object(s).
 
     For more details about Software Heritage PIDs see:
 
     \b
     https://docs.softwareheritage.org/devel/swh-model/persistent-identifiers.html
 
     \b
     Examples:
 
     \b
       $ swh-identify fork.c kmod.c sched/deadline.c
       swh:1:cnt:2e391c754ae730bd2d8520c2ab497c403220c6e3    fork.c
       swh:1:cnt:0277d1216f80ae1adeed84a686ed34c9b2931fc2    kmod.c
       swh:1:cnt:57b939c81bce5d06fa587df8915f05affbe22b82    sched/deadline.c
 
     \b
       $ swh-identify --no-filename /usr/src/linux/kernel/
       swh:1:dir:f9f858a48d663b3809c9e2f336412717496202ab
 
     """
     if verify and len(objects) != 1:
         raise click.BadParameter('verification requires a single object')
 
     results = map(partial(identify_object, obj_type, follow_symlinks), objects)
 
     if verify:
         pid = next(results)[1]
         if verify == pid:
             click.echo('PID match: %s' % pid)
             sys.exit(0)
         else:
             click.echo('PID mismatch: %s != %s' % (verify, pid))
             sys.exit(1)
     else:
         for (obj, pid) in results:
             msg = pid
             if show_filename:
                 msg = '%s\t%s' % (pid, os.fsdecode(obj))
             click.echo(msg)
 
 
 if __name__ == '__main__':
     identify()