Editing _hw.tcl to create memory device for Nios II

Hello,

I am trying to create a custom memory device that the Nios II processor can use as an instruction memory. I connected the Nios II instruction master to my component's avalon mm-slave port but when I build my bsp i get errors telling me that the processor is not connected to any memory device. I have tried to manually edit the _hw.tcl file by using the set_interface_assignment isMemoryDevice true command and then I refreshed my Qsys system. Still, when I build the bsp (in Eclipse using the Nios Software Build Tools) my component is not recognized as a memory device. Any help would be greatly appreciated!!