diff --git a/src/tokens.js b/src/tokens.js
index 98ae8a350..15b4ec0bb 100644
--- a/src/tokens.js
+++ b/src/tokens.js
@@ -166,9 +166,9 @@ async function update(id, values) {
     assert.strictEqual(typeof id, 'string');
     assert.strictEqual(typeof values, 'object');
 
-    let args = [ ];
-    let fields = [ ];
-    for (let k in values) {
+    const args = [ ];
+    const fields = [ ];
+    for (const k in values) {
         fields.push(k + ' = ?');
         args.push(values[k]);
     }