Unable to compile with Crystal v0.32.1

Compilation fails with the following error:

In programs/ttp-cli.cr:153:5

 153 | abort? = ARGV.empty?
       ^
Error: unexpected token: =

OS:

5.3.18-1-MANJARO x86_64 GNU/Linux

Crystal V:

Crystal 0.32.1 (2019-12-18)

LLVM: 9.0.0
Default target: x86_64-pc-linux-gnu