Thank you.  I could not (easily, so I gave up) find information about the compiler switches online.  a) -sv=2009 works and the compiler error disappears b) The assertion AS_TRUE5_STRONG does not fail, as expected, based on the LRM description of "strong". IEEE_Std1800-2017 : 16.12.2 Sequence property Aren't the clock cycles of the sequence which do not complete (because the simulation ends) empty matches?