diff --git a/lib/internal/v8_prof_polyfill.js b/lib/internal/v8_prof_polyfill.js
index eed927f12a9b20..b4c025d50e8b1d 100644
--- a/lib/internal/v8_prof_polyfill.js
+++ b/lib/internal/v8_prof_polyfill.js
@@ -67,13 +67,13 @@ var line = '';
 versionCheck();
 function readline() {
   while (true) {
-    var lineBreak = line.indexOf('\n');
+    const lineBreak = line.indexOf('\n');
     if (lineBreak !== -1) {
-      var res = line.slice(0, lineBreak);
+      const res = line.slice(0, lineBreak);
       line = line.slice(lineBreak + 1);
       return res;
     }
-    var bytes = fs.readSync(fd, buf, 0, buf.length);
+    const bytes = fs.readSync(fd, buf, 0, buf.length);
     line += dec.write(buf.slice(0, bytes));
     if (line.length === 0) {
       return false;