Minecraft Forums

I am try to use the command, fill 644 11 -453 642 11 -453 iron_bars, it will work if I enter it myself, but if I put it in a command block I get, [20:16:21] '' is not a valid number.

Yes, I tested it by typing it into the normal interface first, it worked perfectly, then I put it in the command block, and it tells me that.

Did you try adding "minecraft:iron_bars"

Yeah it gives the same error, but I noticed the numbers in the error are different each time I push the button, so it might be some kind of bug.