spawner display error

I use this command in 16w39b
although it spawns correctly
but its display is wrong

here is the command

/setblock ~ ~1 ~ minecraft:mob_spawner 0 replace {SpawnData:{id:"falling_block",Pos:[1501.5,37.5,1000.5],Block:redstone_block,Data:0,Time:1,DropItem:0},SpawnCount:1,SpawnRange:1,RequiredPlayerRange:25,Delay:1,MinSpawnDelay:100,MaxSpawnDelay:300,MaxNearbyEntities:1}