Border colour around reprojected GeoTIFF is not rendered as transparent one

A GeoTIFF image reprojected from one CRS to another is rendered as it has value of "0" outside of original image boundary:

Steps to reproduce:

1. Define custom CRS in Geoserver:

2. Define simple style:

3. Import attached GeoTIFF file (UM1_OROGRAPHY.tiff) and force CRS to above mentioned

4. Display image as EPSG:3857 or EPSG:4326