sgn fails if the argument is a variable

[britlion]

zxb version 1.4.0-s1980

Code:

dim y as uByte=1
print sgn y
print sgn 2

This wont compile. sgn <number> is fine. sgn variable isn't.

Code:

Traceback (most recent call last):
  File "zxb.py", line 348, in <module>
  File "zxb.py", line 274, in main
  File "ast_\ast.pyc", line 34, in visit
  File "arch\zx48k\translator.pyc", line 340, in visit_UNARY
api.errors.InvalidOperatorError: Invalid operator "SGN"
Build Failed!

Definitely a regression, as it worked fine with an older compiler!