Error when specifying parameters for -mm2_options

[Hazelhuangup]

When I tried to specify the gap open penalty, this error occurs. Even when I specify it to default [4,24], the error remains.
[ERROR] -O and -E must be positive

Is this a bug or am I doing something wrong?

liftoff
-p 10
-o liftoff_gam.out
-f features.list
-mm2_options="-a --end-bonus 5 --eqx -B 12 -O [4,24]"
-s 0.99
-cds \