FORMS_BUILDER_LABEL_MAX_LENGTH affects nothing

[Sashkow]

When I set FORMS_BUILDER_LABEL_MAX_LENGTH in my project's settings.py and then try to add field with label of length higher than 100 via Forms in admin interface, I get an error:

Request Method: | POST
-- | --
http://127.0.0.1:8000/admin/forms/form/add/
2.0.9
DataError
value too long for type character varying(100)
/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/django/db/backends/utils.py  in _execute, line 85
/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/bin/python
3.5.2
['/home/sashkoah/chesno/ukrainian-party-policy-constructor',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python35.zip',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/plat-x86_64-linux-gnu',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/lib-dynload',  '/usr/lib/python3.5',  '/usr/lib/python3.5/plat-x86_64-linux-gnu',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf',  '/home/sashkoah/chesno/ukrainian-party-policy-constructor/env3/lib/python3.5/site-packages/odf']
Mon, 24 Dec 2018 15:35:52 +0000

Should I also do something with database to apply changes?

Upd: I made makemigrations and migrate and now I get the same error when I try to add new field of size above 100, but get a successful outcome when I modify already existing field to the size above 100.