I'm AFB now, so what type of ability is it listed as? Assuming it's not listed as an explicit type (If it's Ex, Su, or Sp, the answer would be obvious, depending on the means you use to take its shape), is it listed on its own or under the creature's spellcasting entry? If the latter, it would depend on whether your DM believes spellcasting is an (Ex) ability. Else, it's up to the DM.
