diff --git a/drivers/comedi/drivers/comedi_test.c b/drivers/comedi/drivers/comedi_test.c
index 01aafce20ef8..4050f66193e5 100644
--- a/drivers/comedi/drivers/comedi_test.c
+++ b/drivers/comedi/drivers/comedi_test.c
@@ -324,10 +324,10 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
 		arg = min(arg,
 			  rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
 		arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
-		if (cmd->scan_begin_arg == TRIG_TIMER) {
+		if (cmd->scan_begin_src == TRIG_TIMER) {
 			/* limit convert_arg to keep scan_begin_arg in range */
 			limit = UINT_MAX / cmd->scan_end_arg;
-			limit = rounddown(limit, (unsigned int)NSEC_PER_SEC);
+			limit = rounddown(limit, (unsigned int)NSEC_PER_USEC);
 			arg = min(arg, limit);
 		}
 		err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg);