diff --git a/swh/scheduler/cli/utils.py b/swh/scheduler/cli/utils.py
index 688965a..4832212 100644
--- a/swh/scheduler/cli/utils.py
+++ b/swh/scheduler/cli/utils.py
@@ -1,90 +1,102 @@
 # Copyright (C) 2019  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
 
 # WARNING: do not import unnecessary things here to keep cli startup time under
 # control
 
 import click
 
 TASK_BATCH_SIZE = 1000  # Number of tasks per query to the scheduler
 
 
 def schedule_origin_batches(scheduler, task_type, origins, origin_batch_size, kwargs):
     from itertools import islice
 
     from swh.scheduler.utils import create_task_dict
 
     nb_origins = 0
     nb_tasks = 0
 
     while True:
         task_batch = []
         for _ in range(TASK_BATCH_SIZE):
             # Group origins
             origin_batch = []
             for origin in islice(origins, origin_batch_size):
                 origin_batch.append(origin)
             nb_origins += len(origin_batch)
             if not origin_batch:
                 break
 
             # Create a task for these origins
             args = [origin_batch]
             task_dict = create_task_dict(task_type, "oneshot", *args, **kwargs)
             task_batch.append(task_dict)
 
         # Schedule a batch of tasks
         if not task_batch:
             break
         nb_tasks += len(task_batch)
         if scheduler:
             scheduler.create_tasks(task_batch)
         click.echo("Scheduled %d tasks (%d origins)." % (nb_tasks, nb_origins))
 
     # Print final status.
     if nb_tasks:
         click.echo("Done.")
     else:
         click.echo("Nothing to do (no origin metadata matched the criteria).")
 
 
 def parse_argument(option):
     import yaml
 
+    if option == "":
+        # yaml.safe_load("") returns None
+        return ""
+
     try:
         return yaml.safe_load(option)
     except Exception:
         raise click.ClickException("Invalid argument: {}".format(option))
 
 
 def parse_options(options):
     """Parses options from a CLI as YAML and turns it into Python
     args and kwargs.
 
     >>> parse_options([])
     ([], {})
     >>> parse_options(['foo', 'bar'])
     (['foo', 'bar'], {})
     >>> parse_options(['[foo, bar]'])
     ([['foo', 'bar']], {})
     >>> parse_options(['"foo"', '"bar"'])
     (['foo', 'bar'], {})
     >>> parse_options(['foo="bar"'])
     ([], {'foo': 'bar'})
     >>> parse_options(['"foo"', 'bar="baz"'])
     (['foo'], {'bar': 'baz'})
     >>> parse_options(['42', 'bar=False'])
     ([42], {'bar': False})
     >>> parse_options(['42', 'bar=false'])
     ([42], {'bar': False})
+    >>> parse_options(['foo', ''])
+    (['foo', ''], {})
+    >>> parse_options(['foo', 'bar='])
+    (['foo'], {'bar': ''})
+    >>> parse_options(['foo', 'null'])
+    (['foo', None], {})
+    >>> parse_options(['foo', 'bar=null'])
+    (['foo'], {'bar': None})
     >>> parse_options(['42', '"foo'])
     Traceback (most recent call last):
       ...
     click.exceptions.ClickException: Invalid argument: "foo
     """
     kw_pairs = [x.split("=", 1) for x in options if "=" in x]
     args = [parse_argument(x) for x in options if "=" not in x]
     kw = {k: parse_argument(v) for (k, v) in kw_pairs}
     return (args, kw)