Did something change about `set_trace_func` between 1.8.7 and 1.9.3?

One of my programs quite working. Here is the basic spec:

  https://github.com/rubyworks/tracepoint/blob/master/spec/trace.rdoc

This works fine in 1.8.7 but not in 1.9.3.

I'm wondering if I should file a bug report.