How to highlight with curly line?

[mooreye]

Currently the master version of Ale highlights with straight line:

Is it possible to switch back to a curly underline like in the 3.3.0 version?

[mooreye]

It seems the highlight group is OK... strange

[mooreye]

hi DiagnosticUnderlineError cterm=undercurl gui=undercurl
hi DiagnosticUnderlineWarn cterm=undercurl gui=undercurl
hi DiagnosticUnderlineInfo cterm=undercurl gui=undercurl
hi DiagnosticUnderlineHint cterm=undercurl gui=undercurl
hi DiagnosticUnderlineOk cterm=undercurl gui=undercurl