USR function (*solved*)

[boriel]

Note: --spectrum parameter does this by default.

--sinclair, you mean? Or are you adding in other machine specific options?

--sinclair, yes (sorry, I'm currently not at home).
Try your program with --sinclair. If it works, you can use either --sinclair or the above trick (remember --sinclair adds more compatibilty with Sinclair BASIC, but also more overhead).