diff --git a/lib/parsers/string.js b/lib/parsers/string.js
index 39f06593c2..cc937de346 100644
--- a/lib/parsers/string.js
+++ b/lib/parsers/string.js
@@ -1,7 +1,11 @@
 'use strict';
 
 const Iconv = require('iconv-lite');
-const decoderCache = new Map();
+const LRU = require('lru-cache');
+
+const decoderCache = new LRU({
+  max: 500,
+});
 
 exports.decode = function (buffer, encoding, start, end, options) {
   if (Buffer.isEncoding(encoding)) {
@@ -9,14 +13,12 @@ exports.decode = function (buffer, encoding, start, end, options) {
   }
 
   const decoderArgs = { encoding, options: options || {} };
-  const decoder =
-    decoderCache.get(decoderArgs) ||
-    decoderCache
-      .set(
-        decoderArgs,
-        Iconv.getDecoder(decoderArgs.encoding, decoderArgs.options),
-      )
-      .get(decoderArgs);
+  const decoderKey = JSON.stringify(decoderArgs);
+  let decoder = decoderCache.get(decoderKey);
+  if (!decoder) {
+    decoder = Iconv.getDecoder(decoderArgs.encoding, decoderArgs.options);
+    decoderCache.set(decoderKey, decoder);
+  }
 
   const res = decoder.write(buffer.slice(start, end));
   const trail = decoder.end();