diff --git a/lib/mbimport.js b/lib/mbimport.js
index 6712be8..c6226d5 100644
--- a/lib/mbimport.js
+++ b/lib/mbimport.js
@@ -157,7 +157,7 @@ var MBImport = (function() {
         buildArtistCreditsFormParameters(parameters, '', release.artist_credit);
 
         if (release['secondary_types']) {
-            for (var i = 0; i < release.secondary_types.length; i++) {
+            for (let i = 0; i < release.secondary_types.length; i++) {
                 appendParameter(parameters, 'type', release.secondary_types[i]);
             }
         }
@@ -188,7 +188,7 @@ var MBImport = (function() {
         appendParameter(parameters, 'comment', release.comment);
 
         // Label + catnos
-        for (var i = 0; i < release.labels.length; i++) {
+        for (let i = 0; i < release.labels.length; i++) {
             let label = release.labels[i];
             appendParameter(parameters, `labels.${i}.name`, label.name);
             appendParameter(parameters, `labels.${i}.mbid`, label.mbid);
@@ -208,7 +208,7 @@ var MBImport = (function() {
         let total_tracks = 0;
         let total_tracks_with_duration = 0;
         let total_duration = 0;
-        for (var i = 0; i < release.discs.length; i++) {
+        for (let i = 0; i < release.discs.length; i++) {
             let disc = release.discs[i];
             appendParameter(parameters, `mediums.${i}.format`, disc.format);
             appendParameter(parameters, `mediums.${i}.name`, disc.title);
@@ -382,7 +382,7 @@ var MBImport = (function() {
             totaltracks += release.discs[i].tracks.length;
         }
         let release_artist = '';
-        for (var i = 0; i < release.artist_credit.length; i++) {
+        for (let i = 0; i < release.artist_credit.length; i++) {
             let ac = release.artist_credit[i];
             release_artist += ac.artist_name;
             if (typeof ac.joinphrase != 'undefined' && ac.joinphrase != '') {