Simulating FIR Compiler II Filters in ModelSim

I have a design that uses a filter built with the MegaWizard FIR Compiler II.

I've been simulating this ModelSim without any problems. My test-bench and all other files are coded in VHDL.

However I have now added support for back pressure flow control. The effect of this is that altera_avalon_sc_fifo is getting instantiated. Although this file existed and was being complied by my simulation script it never actually got instantiated until I added back pressure support.

altera_avalon_sc_fifo is coded in verilog, and my simulation now fails to load, I get the message "ALTERA version supports only a single HDL".

Any ideas on a solution to this?

Mark