NumberFormatException when using negative hexadecimal numbers

[bj0]

I tried switching from google's protobufs to this project for the better kotlin support, but I am running into to issue that appears to be caused by:

optional int32 someVariable = 3 [default = -0x80000000];

Caused by: java.lang.NumberFormatException: For input string: "x80000000"

It looks like #661 fixed this for positive hexadecimal numbers but not negative ones.

[oldergod]

Thanks for reporting