diff --git a/gentong.js b/gentong.js
index 9947709..3fa7b88 100644
--- a/gentong.js
+++ b/gentong.js
@@ -272,14 +272,26 @@ function splitSN(sn, _config) {
     
     var id_count = sn_indexes.length;
     for(var i = 0; i < id_count; i++) {
+        
+        var sn_index = sn_indexes[i];
+        var sn_piece = sn_pieces[sn_index];
+        
         if (sn_pieces[i]) {
-            var sn_index = sn_indexes[i];
-            _sn = _sn + sn_pieces[sn_index];
+            _sn = _sn + sn_piece;
+        } else {
+            logger.warn('Undefined value on sn piece ' + sn_index);
         }
     }
     
-    sn = _sn.trim();
-    logger.info('Got new SN: ' + sn);
+    _sn = _sn.trim();
+    
+    if (_sn) {
+        sn = _sn;
+        logger.info('Got new SN: ' + sn);
+    } else {
+        logger.warn('Got empty SN when using split SN. Use original SN');
+    }
+    
     return sn;
 }