Save as png- layer name changes

I'm using PNG save options to generate a PNG from a psd, but when I run the script the final output changes the layer name that was set in the original file to "layer 0". If I comment out the close command, I can see the layer name stays throughout the entire process, but don't know why the save as would cause the layer name to be lost? Any ideas?

          pngOptions = new  PNGSaveOptions();

          pngOptions.interlaced=false;