diff --git a/src/udev/udev-builtin-net_id.c b/src/udev/udev-builtin-net_id.c
index 5094b95373..f88fa0f71d 100644
--- a/src/udev/udev-builtin-net_id.c
+++ b/src/udev/udev-builtin-net_id.c
@@ -577,10 +577,14 @@ static int get_device_firmware_node_sun(sd_device *dev, uint32_t *ret) {
         if (r < 0)
                 return log_device_debug_errno(dev, r, "Failed to read firmware_node/sun, ignoring: %m");
 
-        r = safe_atou32(attr, ret);
+        uint32_t sun;
+        r = safe_atou32(attr, &sun);
         if (r < 0)
                 return log_device_warning_errno(dev, r, "Failed to parse firmware_node/sun '%s', ignoring: %m", attr);
+        if (sun == 0)
+                return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EINVAL), "firmware_node/sun == 0, ignoring: %m");
 
+        *ret = sun;
         return 0;
 }