diff --git a/benchmark/util/format.js b/benchmark/util/format.js
index 2a4a20097c72d3..44e950a6ca6522 100644
--- a/benchmark/util/format.js
+++ b/benchmark/util/format.js
@@ -25,7 +25,7 @@ function main({ n, type }) {
   const [first, second] = inputs[type || 'string'];
 
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     util.format(first, second);
   }
   bench.end(n);
diff --git a/benchmark/util/inspect-proxy.js b/benchmark/util/inspect-proxy.js
index 3c82d50ac3c0ce..dde86941ff42a3 100644
--- a/benchmark/util/inspect-proxy.js
+++ b/benchmark/util/inspect-proxy.js
@@ -9,7 +9,7 @@ function main({ n }) {
   const proxyA = new Proxy({}, { get: () => {} });
   const proxyB = new Proxy(() => {}, {});
   bench.start();
-  for (var i = 0; i < n; i += 1)
+  for (let i = 0; i < n; i += 1)
     util.inspect({ a: proxyA, b: proxyB }, { showProxy: true });
   bench.end(n);
 }
diff --git a/benchmark/util/inspect.js b/benchmark/util/inspect.js
index fd6f6158cd671d..159d831f762884 100644
--- a/benchmark/util/inspect.js
+++ b/benchmark/util/inspect.js
@@ -30,7 +30,7 @@ const bench = common.createBenchmark(main, {
 
 function benchmark(n, obj, options) {
   bench.start();
-  for (var i = 0; i < n; i += 1) {
+  for (let i = 0; i < n; i += 1) {
     util.inspect(obj, options);
   }
   bench.end(n);
diff --git a/benchmark/util/splice-one.js b/benchmark/util/splice-one.js
index 4ca7c8564d3fc4..6a5a634640add4 100644
--- a/benchmark/util/splice-one.js
+++ b/benchmark/util/splice-one.js
@@ -25,7 +25,7 @@ function main({ n, pos, size }) {
   }
 
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     spliceOne(arr, index);
     arr.push('');
   }
diff --git a/benchmark/util/type-check.js b/benchmark/util/type-check.js
index f11471980d9216..5b992e729e63ae 100644
--- a/benchmark/util/type-check.js
+++ b/benchmark/util/type-check.js
@@ -45,7 +45,7 @@ function main({ type, argument, version, n }) {
   const arg = args[type][argument];
 
   bench.start();
-  for (var i = 0; i < n; i++) {
+  for (let i = 0; i < n; i++) {
     func(arg);
   }
   bench.end(n);