diff --git a/lib/perf_hooks.js b/lib/perf_hooks.js
index 18b0332feaffaa..1094d763236ff3 100644
--- a/lib/perf_hooks.js
+++ b/lib/perf_hooks.js
@@ -313,7 +313,7 @@ class PerformanceObserver extends AsyncResource {
     const observerCountsGC = observerCounts[NODE_PERFORMANCE_ENTRY_TYPE_GC];
     const types = this[kTypes];
     const keys = Object.keys(types);
-    for (var n = 0; n < keys.length; n++) {
+    for (let n = 0; n < keys.length; n++) {
       const item = types[keys[n]];
       if (item) {
         L.remove(item);
@@ -343,7 +343,7 @@ class PerformanceObserver extends AsyncResource {
     this[kBuffer][kEntries] = [];
     L.init(this[kBuffer][kEntries]);
     this[kBuffering] = Boolean(options.buffered);
-    for (var n = 0; n < entryTypes.length; n++) {
+    for (let n = 0; n < entryTypes.length; n++) {
       const entryType = entryTypes[n];
       const list = getObserversList(entryType);
       if (this[kTypes][entryType]) continue;