darktable export to TIFF bug?

With darktable 2.4.1 on Windows 8.1, I tried to export to “pbpx_dt.tiff” (with 2 f’s) but DT changed the name and exported to “pbpx_dt.tif” (with one f).

Is this a bug or a feature?

f:\prose\PICTURES>c:\programfiles\darktable\bin\darktable-cli pbpx_ctm.dng pbpx_dt.tiff  2>pbpx_dt.lis

[export_job] exported to `pbpx_dt.tif'

I don’t know if it is a bug, but nobody care about bugs in old version. Darktable 2.4.1 is from 22. January 2018 we are at the moment at version 2.6.2.

When I save an image with Irfanview as TIFF, the file ends with .tif
Don’t think it’s a bug

No bugs, I confirm that the tiff file extension is .tif