Can't synthesize Nios II without IP license

I'm trying to evaluate a Nios II design using Quartus II 11.1 sp1. I get the following error from Quartus:

Error (204012): Can't generate netlist output files because the file <file> is an OpenCore Plus time-limited file

The KB says to turn off IBIS file generation to fix this but it's not on.

All the documentation says that I should be able to evaluate a Nios II core without having to buy the license first.