@laanwj Note that the sizes are verified in the tests:
```
 ["-2147483647", "0x04 0xFFFFFFFF EQUAL"],
 ["-2147483648", "0x05 0x0000008080 EQUAL"],
```
That's confusing at first glance, but see what @maaku said above. -2147483647 is -0x7FFFFFFF, sent over the wire as 0xFFFFFFFF. So that's the minimum value of a 4-byte operand.

I suppose it would be helpful to verify the operand bounds explicitly in the tests as well:
valid: ```["-2147483647", "1ADD 2147483646 EQUAL"]```
invalid: ```["-2147483648", "1ADD 1"]```

I'll double-check that those aren't already there and push that up.