diff --git a/test/dm/panel.c b/test/dm/panel.c
index a840fb4..49f5ac7 100644
--- a/test/dm/panel.c
+++ b/test/dm/panel.c
@@ -40,7 +40,7 @@
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
 	ut_asserteq(1000, period_ns);
-	ut_asserteq(170 * 1000 / 256, duty_ns);
+	ut_asserteq(170 * 1000 / 255, duty_ns);
 	ut_asserteq(true, enable);
 	ut_asserteq(false, polarity);
 	ut_asserteq(1, sandbox_gpio_get_value(gpio, 1));
@@ -49,29 +49,29 @@
 	ut_assertok(panel_set_backlight(dev, 40));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(64 * 1000 / 256, duty_ns);
+	ut_asserteq(64 * 1000 / 255, duty_ns);
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_MAX));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(255 * 1000 / 256, duty_ns);
+	ut_asserteq(255 * 1000 / 255, duty_ns);
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_MIN));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(0 * 1000 / 256, duty_ns);
+	ut_asserteq(0 * 1000 / 255, duty_ns);
 	ut_asserteq(1, sandbox_gpio_get_value(gpio, 1));
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_DEFAULT));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
 	ut_asserteq(true, enable);
-	ut_asserteq(170 * 1000 / 256, duty_ns);
+	ut_asserteq(170 * 1000 / 255, duty_ns);
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_OFF));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(0 * 1000 / 256, duty_ns);
+	ut_asserteq(0 * 1000 / 255, duty_ns);
 	ut_asserteq(0, sandbox_gpio_get_value(gpio, 1));
 	ut_asserteq(false, regulator_get_enable(reg));