uMap Minimap Zoom Control With Watercolor Tiles

Using Watercolor tiles in uMap.

The minimap appears to display a zoom level greater than the main map as expected, but only when the main map is between zoom levels 6-18.

Between zoom levels 0-5 the minimap does not display any continents.

However when using another tile set such as Lyrk, the minimap does display continents with all zoom levels of the main map.

Is there a way to achieve the display of continents in the minimap, at all zoom levels of the main map using the Watercolor tiles ?