Hello, I now detected the following problem. The script below runs in gretl 1.9.11, but will cause gretl 2016a to crash (I am using ubuntu 12.04, gretl 2016a is in a virtualbox). nulldata 10 function series f1(series z) series s=1 loop i=1..1 s[1]=0 endloop return s end function function scalar f2(matrix *my,matrix *ma) series z=1 series f=f1(z) return 1 end function series y=0 matrix my=ones(10,1) matrix par=1 scalar a=BFGSmax(par,f2(&my,&par)) series yy=0 series x=f1(y) Oddly, if I add a line between the final two and that new line defines a series (e.g. series yy=0), it will not crash. Additionally, if I comment out s[1]=0 in f1 or comment out loop i=1..1 and the corresponding endloop, it will also not crash. Thanks, Pedro