Would R-core be receptive to adding an additional parameter to stopifnot so we can hide the call in the output as in stop? i.e. The signature would become: stopifnot2 <- function (..., exprs, exprObject, local = TRUE, .call = TRUE) It looks like this would be a one-line change to the the underlying stop call to: stop(simpleError(msg, call = if((p <- sys.parent(1L)) && isTRUE(.call)) sys.call(p))) Best Tim