Partlces - That entity cannot be found

Hello,

Using a custom spawner

/setblock ~ ~ ~1 mob_spawner 0 replace {EntityId:WitherSkull,Delay:1,SpawnData:{direction:[],Invulnerable:1b}}

, every time I try to execute this command :

/particle cloud ~ ~ ~ 0 0.5 0 0.1 5 @e[type=WitherSkull]

I get 6 times (6 errors each time I execute the 1 command) "That entity cannot be found"

Just to be sure :

/kill @e[type=WitherSkull]

I get 6 times "Killes entity.WitherSkull.name" so seems like particle command founded the entity but the error says the opposite.

Thanks

Korko