Lightmaps not saving in irredit

[NoisyPerlin]

Hi, I'm having some problems with lightmaping in irredit. I've got a simple scene, with a mesh. I use the lightmapper, and I see the light maps generated, both on the viewscreen and on the list of textures. The list of textures shows the generated lightmaps as "#unsaved_lightmap1". So far, so good. However, when I save the scene, no textures are saved for the lightmap, only for the object and the .irr file. So, irrlicht can load the scene ok, but it has no lightmapping information. I'm sure that there's something that I should be doing in irredit so that it saves those lightmap textures, but I haven't a clue what I'm missing. Can anyone tell me what I'm doing wrong?