Image asset not recognized in interface builder

I added an asset catalog to an old iOS project that I'm in the process of updating. The app was originally created before asset catalogs existed.

I added an image and an icon set to my catalog. The icon works, and the image shows up when I run the app, but Interface Builder doesn't recognize the image by name when I type it into the Image field on an imageview.

I'm guessing that there is something somewhere which causes interface builder to read an asset catalog, which is probably not set on my old project, but I can't figure out what it is.

Thanks, Frank