Cannot reuse custom tagtrees directories

[MyFedora]

Default tagtrees directory

$ filetags --tagtrees
INFO     Creating tagtrees and their links. It may take a while …  (exponentially with respect to number of tags)
INFO     Number of links created in "/home/user/.filetags_tagfilter" for the 5 files: 5  (tagtrees depth is 2)
$ filetags --tagtrees
INFO     Creating tagtrees and their links. It may take a while …  (exponentially with respect to number of tags)
INFO     Number of links created in "/home/user/.filetags_tagfilter" for the 5 files: 5  (tagtrees depth is 2)

Custom tagtrees directory

$ filetags --tagtrees --tagtrees-dir custom
INFO     Creating tagtrees and their links. It may take a while …  (exponentially with respect to number of tags)
INFO     Number of links created in "custom" for the 5 files: 5  (tagtrees depth is 2)
$ filetags --tagtrees --tagtrees-dir custom
ERROR    The given tagtrees directory custom is not empty. Aborting here instead of removing its content without asking. Please free it up yourself and try again.

Expectation

$ filetags --tagtrees --tagtrees-dir custom
INFO     Creating tagtrees and their links. It may take a while …  (exponentially with respect to number of tags)
INFO     Number of links created in "custom" for the 5 files: 5  (tagtrees depth is 2)
$ filetags --tagtrees --tagtrees-dir custom
INFO     Creating tagtrees and their links. It may take a while …  (exponentially with respect to number of tags)
INFO     Number of links created in "custom" for the 5 files: 5  (tagtrees depth is 2)