diff --git a/lib/mysql.js b/lib/mysql.js
index 5f3cafc..b04e190 100644
--- a/lib/mysql.js
+++ b/lib/mysql.js
@@ -215,9 +215,13 @@ MySQL.prototype.updateOrCreate = function (model, data, callback) {
       } else {
         v = data[key];
       }
-      fieldsNames.push(k);
-      fieldValues.push(v);
-      if (!mysql.id(model, key)) combined.push(k + ' = ' + v);
+      if (v !== undefined) {
+        fieldsNames.push(k);
+        fieldValues.push(v);
+        if (!mysql.id(model, key)) {
+          combined.push(k + ' = ' + v);
+        }
+      }
     }
   });