Allocation when sorting a view

Just reading through “In place sorting for views” and cannot wrap my head around the following allocations in my case:

x = [2,1,10,15,20]

@btime sort!(view($x, 2:4))
53.308 ns (2 allocations: 96 bytes)

To check I also tried the following, which looks fine:

@btime sort!($x)
29.256 ns (0 allocations: 0 bytes)

@btime view($x, 2:4)
2.933 ns (0 allocations: 0 bytes)

I have allocations for the in-place view sort on both 1.7.3 and 1.8.0. I’m surprised this didn’t work, so I’m probably missing something stupid here?