Error undefined symbol SC_0

When I compile the following function as
a .c file, it compiles fine.

But when I compile it to a .SRC file,
and then have it assembled, the symbol
?SC_0 is undefined. This symbol is
apparently a compiler generated symbol,
so why should it be undefined?

It exists when I compile with the C compiler,
so I know it's OK for it to be there.

Is there any workaround for this?

I'm already including C51l.lib - do I need
to include another lib?

Anyway, here is the code snippet:

void DownloadFirmware ( unsigned char far * flAddr )
{
Byte * startOfRAM;
Byte * topOfRAM;
// for loader code that will
// be running in RAM
Ushort addr, new_addr, delta, i ;
Uchar lo_byte ;
Uchar* index ;
Uchar instruction ;
Uchar length;
Uchar instr_len [ ] =
{
1, 2, 3, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
3, 2, 3, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
3, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
3, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2, 2, 2, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2, 2, 2, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2, 2, 2, 3, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2, 2, 2, 1, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 1, 1, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
3, 2, 2, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2, 2, 2, 1, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
2, 2, 2, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
2, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
2, 2, 2, 1, 1, 3, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2,
1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
} ;

And generated code:
00000B 7800 F 509 MOV R0,#LOW (instr_len?051)
00000D 7C00 F 510 MOV R4,#HIGH (instr_len?051)
00000F 511 MOV R5,#?SC_0
*** ________________________________________________^
*** ERROR #A45 IN 511 (downloadfirm.src, LINE 511): UNDEFINED SYMBOL
000011 7B00 F 512 MOV R3,#BYTE2 (_?ix1000)
000013 7A00 F 513 MOV R2,#HIGH (_?ix1000)
000015 7900 F 514 MOV R1,#LOW (_?ix1000)
000017 7E01 515 MOV R6,#01H
000019 7F00 516 MOV R7,#00H
00001B 120000 E 517 LCALL ?C?COPY

Thanks,

Ed