[rules-users] "==" not work for big int value

Hi, I'm using Drools 4.0.7. I find "==" operator does not work for big int value (like 2147483647). The condition is like "sec.fir.i == 2147483647". I attach my test code. With my simple testing, it seems that it does not work for comparsion with int constant from 1000000001 to 2147483647. Is it a bug of drools? I have already tested long and BigInteger do not have this kind of problem. Thanks!