set linetrace on not working? #39

I'm trying out the tutorial example and got nothing:
/home/netflow/dev/triangle.rb:6
0.upto(n) do |i|
(rdb:1) p tri
0
(rdb:1) display tri
1: tri = 0
(rdb:1) display i
2: i =
(rdb:1) set linetrace on
line tracing is on.
(rdb:1) finish
6

I'm expecting

(rdb:1) display i
2: i =
(rdb:1) set linetrace on
line tracing is on.
(rdb:1) finish
Tracing(1):triangle.rb:7 tri += i
1: tri = 0
2: i = 0
Tracing(1):triangle.rb:7 tri += i
1: tri = 0
2: i = 1
Tracing(1):triangle.rb:7 tri += i
1: tri = 1
2: i = 2
Tracing(1):triangle.rb:7 tri += i
1: tri = 3
2: i = 3
Tracing(1):triangle.rb:9 return tri
1: tri = 6
2: i =