Type mismatch on IF statement

This used to work in AMOS 2, and works in AMOS Pro, but not in AOZ:

k$=inkey$
if (k$="." or (mouse zone=5 and mouse key<>0)) and gridzoom<=10
  print "yes"
else
  print "no"
end if

Compiling e:/Data/My Documents/AOZ Studio Applications/applications/TestAOZ, emulation: PC, speed: fast.

First pass...

main.aoz:2:44: error: type mismatch

If I change it to this, it fails differently, but still works in AMOS Pro:

k$=inkey$
gridzoom=2
if (k$="." or (mouse zone=5 and mouse key<>0)) and gridzoom<=10 then print "yes"

Compiling e:/Data/My Documents/AOZ Studio Applications/applications/TestAOZ, emulation: PC, speed: fast.

First pass...

undefined is not a function

TypeError: undefined is not a function

at firstPass (C:\snapshot\aoz\compiler\compiler.js)

... (usual c:\snapshot error lines)