diff --git a/quicksettings/flashlight/kauth/flashlighthelper.cpp b/quicksettings/flashlight/kauth/flashlighthelper.cpp
index b77430bc..e33cc203 100644
--- a/quicksettings/flashlight/kauth/flashlighthelper.cpp
+++ b/quicksettings/flashlight/kauth/flashlighthelper.cpp
@@ -28,13 +28,34 @@ public Q_SLOTS:
 
 KAuth::ActionReply Flashlighthelper::setbrightness(const QVariantMap &args)
 {
-    const char *sysPath = args.value("sysPath"_L1).toString().toUtf8().constData();
-    const char *brightness = args.value("brightness"_L1).toString().toUtf8().constData();
+    // Store as named QByteArrays so constData() pointers remain valid for the
+    // duration of the function. The originals were temporaries that were
+    // destroyed at the end of each declaration statement.
+    // (need to double-check this, but seems likely to be the cause of the random failures
+    // we were seeing in testing)
+    const QByteArray sysPathBytes = args.value("sysPath"_L1).toString().toUtf8();
+    const QByteArray brightnessBytes = args.value("brightness"_L1).toString().toUtf8();
+
+    if (sysPathBytes.isEmpty()) {
+        qCWarning(FLASHLIGHTHELPER) << "sysPath argument is missing or empty";
+        return KAuth::ActionReply::HelperErrorReply();
+    }
 
     struct udev *udev = udev_new();
-    struct udev_device *device = udev_device_new_from_syspath(udev, sysPath);
+    if (!udev) {
+        qCWarning(FLASHLIGHTHELPER) << "Failed to create udev context";
+        return KAuth::ActionReply::HelperErrorReply();
+    }
 
-    int ret = udev_device_set_sysattr_value(device, "brightness", const_cast<char *>(brightness));
+    struct udev_device *device = udev_device_new_from_syspath(udev, sysPathBytes.constData());
+    if (!device) {
+        qCWarning(FLASHLIGHTHELPER) << "Failed to find udev device for syspath:" << sysPathBytes;
+        udev_unref(udev);
+        return KAuth::ActionReply::HelperErrorReply();
+    }
+
+    // The libudev header declares value as const char*, so no cast needed.
+    int ret = udev_device_set_sysattr_value(device, "brightness", brightnessBytes.constData());
 
     udev_device_unref(device);
     udev_unref(udev);
@@ -42,7 +63,7 @@ KAuth::ActionReply Flashlighthelper::setbrightness(const QVariantMap &args)
     if (ret >= 0) {
         return KAuth::ActionReply::SuccessReply();
     } else {
-        qCWarning(FLASHLIGHTHELPER) << "Failed to set udev system attribute";
+        qCWarning(FLASHLIGHTHELPER) << "Failed to set udev system attribute, errno:" << -ret;
         return KAuth::ActionReply::HelperErrorReply();
     }
 }