Extern function in Inline Assembly

I need to migrate my project from ARM Compiler 5 to ARM Compiler 6

How can I write extern syntax in inline assembly function?

Original Compilable Code In AC5

void myFuction() {}
__asm void AssemblyFunction()
{
    extern myFuction
}

My Code in AC6

void myFunction() {...}
void myInlineAssemblyFunction()
{
    __ASM("extern myFunction"); //importing extern outside function
}

It seems that the AC6 can't compile this part of importing extern outside function.