Quartus II 7.2 & Declaring bus range problem

I've design my project with some .vhd and .bdf files without any error or warnings but in "synthesis and elaborate" I face to this problem frequently:

Warning: Undeclared parameter MTU

Error: Bus range for signal "port "label_out[MTU-1..MTU-32]" (ID FWD_Input_BDF:inst1)" must be a number

but I've specified that in the .vhd file in generic clause

for example like this:

generic (MTU :integer:=8192);

and I've updated my designs and block/symbols frequent times but nothing has changed

I couldn't find somewhere else for declaring the value