TracePoints with incompatible events (i.e. events not in ISEQ_TRACE_EVENTS) with a method target will fail an assertion error because it does not filter for the supported events. For example, the following lines will cause an assertion error: def foo; end # No arguments passed into TracePoint.new enables all ISEQ_TRACE_EVENTS TracePoint.new {}.enable(target: method(:foo)) # Raise is not supported with a target TracePoint.new(:raise, :return) {}.enable(target: method(:foo)) foo Crashes with: Assertion Failed: vm_insnhelper.c:7026:vm_trace:(iseq_local_events & ~(0x0001 | 0x0002 | 0x0004 | 0x0008 | 0x0010| 0x0020| 0x0040 | 0x0100 | 0x0200 | 0x4000 | 0x010000| 0x020000)) == 0