diff --git a/brightnessctl.c b/brightnessctl.c
index 7b88a53..cc2b2d7 100644
--- a/brightnessctl.c
+++ b/brightnessctl.c
@@ -370,7 +370,7 @@ float val_to_percent(float val, struct device *d, bool rnd) {
 }
 
 unsigned long percent_to_val(float percent, struct device *d) {
-	return roundf(powf(percent / 100, p.exponent) * d->max_brightness);
+	return roundf(powf(fmaxf(percent, 0) / 100, p.exponent) * d->max_brightness);
 }
 
 void print_device(struct device *dev) {