Combining large map size (e.g. poke(0x5f56,0x80,0)) with the new return value for out-of-bounds mget poke(0x5f36,0x10) poke(0x5f5a,255) causes any tile 128+ to be returned as the defined return value instead of the actual map tile.

Map width 256: Unable to interact with blocks and treetop rendering does not detect tree tiles anymore.

If map width is less than 128, tiles from map edge to 128 return zero and 128+ return the defined return value.

At 128 tiles:

Thanks @cubee -- that was a rather silly oversight! Fixed for 0.2.5d