Memory Initialization File for multiple RAMs

Ok I got it so far. I am using the M4K memory within an other design unit. Here is the simplified code:

module LocalMem(...);
parameter cpuid = 0;
M4K memory (
    .clock(clk),
    .data(m4k_data),
    .rdaddress(m4k_rdaddress),
    .wraddress(m4k_wraddress),
    .wren(m4k_wren),
    .q(m4k_q)
    );
defparam memory.altsyncram_component.init_file = {"mem", cpuid, ".mif"};
endmodule
module TestLocalMem(...);
LocalMem# (.cpuid(1)) localmem_inst(...);
endmodule

This does not work. Within the defparam line, cpuid seems to be empty. No matter what I set cpuid to, the file "mem.mif" gets loaded. I have also tried this to make cpuid the correct ASCII value:

defparam memory.altsyncram_component.init_file = {"mem", 8'd48 + cpuid, ".mif"};

but no change...

Maybe you have another hint for me?