LINK_URL_MAX_LENGTH undefined when module is disabled

I get this PHP notice

Notice: Use of undefined constant LINK_URL_MAX_LENGTH - assumed 'LINK_URL_MAX_LENGTH' in link_field_schema() (line 16 of /srv/example.com/sites/all/modules/link/link.install).

This happens only on first pageload after I clear Drupal's cache. It seems the install function does not have access to the constant definition in the .module-file. On subsequent page loads, this warning goes away - presumably because the necessary constant is properly defined/cached by then.

This is on a clean D7 installation.