diff --git a/lib/mysql.js b/lib/mysql.js
index 335f4dd..c34c026 100644
--- a/lib/mysql.js
+++ b/lib/mysql.js
@@ -403,7 +403,7 @@ MySQL.prototype.alterTable = function (model, actualFields, actualIndexes, done,
     propNames.forEach(function (propName) {
         if (propName === 'id') return;
         var found;
-        if (actualIndexes) {
+        if (actualFields) {
             actualFields.forEach(function (f) {
                 if (f.Field === propName) {
                     found = f;