diff -Naur xfce4-power-manager-1.6.1_orig/common/xfpm-brightness.c xfce4-power-manager-1.6.1/common/xfpm-brightness.c
--- xfce4-power-manager-1.6.1_orig/common/xfpm-brightness.c	2017-11-24 01:52:06.000000000 +0200
+++ xfce4-power-manager-1.6.1/common/xfpm-brightness.c	2019-07-06 21:24:10.987675534 +0300
@@ -361,7 +361,7 @@
 	brightness->priv->helper_has_hw = FALSE;
     } else {
 	brightness->priv->helper_has_hw = TRUE;
-	brightness->priv->min_level = 0;
+	brightness->priv->min_level = 1;
 	brightness->priv->max_level = ret;
 	brightness->priv->step =  ret <= 20 ? 1 : ret / 10;
     }
diff -Naur xfce4-power-manager-1.6.1_orig/src/xfpm-backlight.c xfce4-power-manager-1.6.1/src/xfpm-backlight.c
--- xfce4-power-manager-1.6.1_orig/src/xfpm-backlight.c	2017-11-24 01:52:06.000000000 +0200
+++ xfce4-power-manager-1.6.1/src/xfpm-backlight.c	2019-07-06 21:33:11.435658629 +0300
@@ -156,19 +156,20 @@
 {
     gchar *summary;
 
+    /* generate a human-readable summary for the notification */
+    summary = g_strdup_printf (_("Brightness: %.0f percent"), value);
     /* create the notification on demand */
     if ( backlight->priv->n == NULL )
-    {
-        /* generate a human-readable summary for the notification */
-        summary = g_strdup_printf (_("Brightness: %.0f percent"), value);
         backlight->priv->n = xfpm_notify_new_notification (backlight->priv->notify,
                                                            _("Power Manager"),
                                                            summary,
                                                            XFPM_DISPLAY_BRIGHTNESS_ICON,
                                                            0,
-                                                           XFPM_NOTIFY_NORMAL);
-        g_free (summary);
-    }
+                                                           XFPM_NOTIFY_NORMAL);
+    else
+        notify_notification_update (backlight->priv->n, _("Power Manager"), summary, XFPM_DISPLAY_BRIGHTNESS_ICON);
+
+    g_free (summary);
 
     /* add the brightness value to the notification */
     notify_notification_set_hint (backlight->priv->n, "value", g_variant_new_int32 (value));