"primitive conversion" panic

[palfrey]

This is a build based off of #13 but I didn't think it would break things this badly. Any idea how to solve this one?

thread 'build_zsh' panicked at 'primitive conversion', /home/palfrey/.cargo/git/checkouts/hstrace-de21f6094a22c832/6f7a453/src/call/mod.rs:29:1
stack backtrace:
   0:     0x55a9180c334c - <unknown>
   1:     0x55a9180ede5c - <unknown>
   2:     0x55a9180bb1a8 - <unknown>
   3:     0x55a9180c5927 - <unknown>
   4:     0x55a9180c55df - <unknown>
   5:     0x55a9180c618b - <unknown>
   6:     0x55a9180c5e77 - <unknown>
   7:     0x55a9180c3814 - <unknown>
   8:     0x55a9180c5b89 - <unknown>
   9:     0x55a9180ec203 - <unknown>
  10:     0x55a9180ec0c1 - <unknown>
  11:     0x55a9180ec06b - <unknown>
  12:     0x55a9180ebdb6 - <unknown>

(lots more frames with <unknown>)