Error message when exporting sprite to PNG

When trying to export to PNG, I get an error:
libpng: Wrote palette index exceeding num_palette
Error saving frame 1 in the file “[File path].png”

The file comes out seemingly fine, but when I try to import it into certain programs it causes them to crash.
The image is in Indexed colour, with 13 colours.

Can you show me what it looked like before you exported it… like the aseprite file?