Fix #1613, again (but this is a different bug).
Fix #1613, again (but this is a different bug).

diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark