diff --git a/lib/system.js b/lib/system.js
index befdb3e..bdb1b6b 100644
--- a/lib/system.js
+++ b/lib/system.js
@@ -124,7 +124,7 @@ function system(callback) {
             try {
               const lines = execSync('sysctl -i kern.hostuuid kern.hostid', util.execOptsLinux).toString().split('\n');
               result.uuid = util.getValue(lines, 'kern.hostuuid', ':').toLowerCase();
-              if (!result.serial) {
+              if (!result.serial || result.serial === '-') {
                 result.serial = util.getValue(lines, 'kern.hostid', ':').toLowerCase();
               }
             } catch (e) {