Cannot add second ingredient to booze barrel

I thought i'd try out brewing, but i can't get it to work.

I place the booze barrel on the wooden scaffold
I right click the booze barrel with water cells, water buckets, sugar cane, wheat, everything goes fine
But when i try to add a second ingredient, nothing happens. I can still add more of the first tho.
Fermenting goes fine, i can tap it and drink it but it's not exactly the best sort with only 1 ingredient type. Am i missing a step?

Minecraft 1.2.5 Mods:

Industrialcraft 1.97
Buildcraft 3.1.5
Forestry 1.4.8.6
Railcraft 5.4.7b
Forge 3.3.8.152
IDresolver + patch for forge
journeymap 1.5.3

Okay, it's working with hops and wheat, i guess you're just not supposed to add water when making rum. Thank you!