diff --git a/lib/iolog/iolog_timing.c b/lib/iolog/iolog_timing.c
index c933b4ca8..4fba08d62 100644
--- a/lib/iolog/iolog_timing.c
+++ b/lib/iolog/iolog_timing.c
@@ -55,6 +55,12 @@ iolog_adjust_delay(struct timespec *delay, struct timespec *max_delay,
 {
     debug_decl(iolog_adjust_delay, SUDO_DEBUG_UTIL);
 
+    /* Avoid division by zero or negative delays. */
+    if (scale_factor <= 0.0) {
+	sudo_timespecclear(delay);
+	debug_return;
+    }
+
     if (scale_factor != 1.0) {
 	/* Order is important: we don't want to double the remainder. */
 	const double seconds = (double)delay->tv_sec / scale_factor;
diff --git a/plugins/sudoers/sudoreplay.c b/plugins/sudoers/sudoreplay.c
index d4aa2662c..5f81111a9 100644
--- a/plugins/sudoers/sudoreplay.c
+++ b/plugins/sudoers/sudoreplay.c
@@ -287,7 +287,7 @@ main(int argc, char *argv[])
 	case 's':
 	    errno = 0;
 	    speed_factor = strtod(optarg, &ep);
-	    if (*ep != '\0' || errno != 0)
+	    if (*ep != '\0' || errno != 0 || speed_factor < 0.0)
 		sudo_fatalx(U_("invalid speed factor: %s"), optarg);
 	    break;
 	case 'V':
@@ -795,8 +795,7 @@ get_timing_record(struct replay_closure *closure)
 
 	if (nodelay) {
 	    /* Already waited, fire immediately. */
-	    timing->delay.tv_sec = 0;
-	    timing->delay.tv_nsec = 0;
+	    sudo_timespecclear(&timing->delay);
 	} else {
 	    /* Adjust delay using speed factor and max_delay. */
 	    iolog_adjust_delay(&timing->delay, closure->max_delay,