Integer overflow error

Hi, everyone

I found some error in hashcat 4.0.1
I'm sure it is bug on 4.0.1 version , is't it?

[hashcat-3.30] ./hashcat64.bin -a 3  ?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a --keyspace
13647689206181

[hashcat-4.0.1] ./hashcat64.bin -a 3  ?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a --keyspace
Integer overflow detected on keyspace of mask:   ?a?a?a?a?a?a?a?a?a?a?a?a?a?a?a

0