TASM macro args can't be embedded in identifiers

I'm using TASM 3.2 (Telemark Assembler, *not* Borland Turbo Assembler)
to assemble code for the z80. I can't find the syntax to embed a macro
argument in an identifier, like I can in MASM, where I just surround
the argument name with ampersands.

This is what I want to do (TASM code with MASM-style embedding):
#define macro1(arg) prefix_&arg&: \ ld a, 0
macro1(foo)
  jp prefix_foo ; test that label was created correctly

prefix_&arg& should become prefix_foo, but TASM barfs. I've searched
all over, but can't find this documented for TASM. Has anybody else
had to do this before?

Thanks in advance,
Alek