Usage of short options with argument keeps unneeded equal sign

[kzmkv]

Small example:

➤  cat example.py
"""Example

Usage:
  example.py [options] <name>...

Options:
  -s=<kn>, --speed=<kn> Speed in km.
"""

from docopt import docopt

args = docopt(__doc__)
print(args)

Using long option:

➤  python3.5 example.py --speed=25 name
{'--speed': '25',
 '<name>': ['name']}

Using short option:

➤  python3.5 example.py -s=25 name
{'--speed': '=25',
 '<name>': ['name']}

Note that --speed value starts from an unneeded equal sign.

[TylerTemp]

short option can stick value together, but no = needed.

python3.5 example.py -s25 name

equals

python3.5 example.py -s 25 name

equals

python3.5 example.py --speed=25 name

equals

python3.5 example.py --speed 25 name

[bittner]

But why is specifying -s=<kn> even accepted in the docstring?

Isn't the specification in the docstring invalid, and docopt should tell us?