elab optional syntax doesn't work

Stream: lean4

[jthulhu]

Consider the following MWE

elab "#glob " l:(ident "&")? : command => do
  dbg_trace "l = {l}"

#glob     -- l = none
#glob x & -- l = none

I'm not sure this is the expected behavior. I would expect, in the second case, that l is some syntax tree.