Getting UE to recognize DDS files as Texture Cubes?

I’m trying to import .dds files into UE4, and the assets are coming IN okay… but they’re recognized as TEXTURES rather than as TEXTURE CUBES, and thus the engine won’t let me assign them to slots that take cubemaps.

I’ve got the format correct (I know I must or the import would fail, since only the one format is supported for DDS), but something else must be wrong.

And no, I can’t just follow the manual’s instructions, since that requires having Photoshop and I use GIMP. There’s obviously something there that’s got UE4 making the distinction, but I can’t figure out what it is…?