Type selector in commands doesn't work properly

I was using the teleport command to teleport some mobs
I wanted to make a spell (with command blocks) that teleports everything serveral blocks in the air, everything besides players and items. So I used this command: tp @e[type=!Item,type=!Player] ~ ~20 ~

When i tried this i saw items get teleported too eventhough i used a exclamation mark... All other types of entities did get teleported to...

1. Place down a command block with a redstone input
2. Use the command " tp @e[type=!Item,type=!Player] ~ ~20 ~ " in the command block
3. Throw some items on the ground, spawn some mobs
4. Trigger the redstone input