Fill command fails when using End Portal as the first argument in a replace query

It would appear that the fill command attempts to read 'minecraft:end_portal' as a data tag when used as the block in the fill command. Everything else seems to work, just this specific block in this specific order.

Here's the command that caused the failure.

/fill ~ ~2 ~ ~2 ~2 ~2 minecraft:end_portal 0 replace minecraft:air