Internal compiler error: Use of unknown variable

[nqpz]

The Futhark program

def numbers: []i32 = [ 100 ] ++ (0..<10)
entry main = numbers

gives me the error message

After internalisation:
In expression of statement
  {dim_match_5172 : ({}, bool)}
In subexp d₈_4500
Use of unknown variable d₈_4500.

with futhark c from git.

[athas]

How strange. I remember fixing bugs like this before.