Import error

[Carlo]

Hi everyone,
i'm having trouble with the statement import. Here is an example:

//file ~/d/libtest.d
int fun(int x){
     return x;
}
//endfile

//file ~/d/test.d
import std.stdio;
import libtest;

void main(){
     writeln(fun(2));
}
//endfile


I issue the commands
#cd ~/d
#dmd test.d

and i get the error

test.d:(.text._Dmain+0x9): undefined reference to `_D7libtest3funFiZi'
collect2: ld returned 1 exit status
--- errorlevel 1

I have no troubles with standard libraries, just mine's. I have the dmd 
2.0.50 compiler on a GNU/Linux 64bit system. Any idea?